DPP C2(b)
Kolej Kemahiran Tinggi Mara
Masjid Tanah, Melaka
INFORMATION SHEET
PROGRAMME DIPLOMA IN AUTOMOTIVE ENGINEERING TECHNOLOGY
SESSION
CODE & COURSE SEMESTER 2
LECTURER
DVA 20212 ELECTRICAL & SHEET NO IS 06
ELECTRONIC FUNDAMENTAL
WEEK 6
TOPIC 1.0 Basic Electrical Principles
SUB-TOPIC
1.11 Kirchoff’s Law
TOPIC 1.12 Electromagnetism and Magnetic Circuit
LEARNING
OUTCOME After the lesson, student should be able to:
1. Apply concept of Kirchhoff’s law.
2. Describe electromagnetism and magnetic circuit.
3. Use electromagnetism board to explain the electromagnetism
concept.
4. Create magnetic circuit.
1.11 Kirchoff’s Law
Electric circuits are divided into series circuit, parallel circuit and series/parallel circuit
according to connecting method. The sum of input current and output current are equal in
this circuit.
Also, impressed voltage and sum of voltage drop is same, this is Kirchoff’s law.
There are two laws in Kirchoff's law.
1.11.1 Kirchoff’s current law (Kirchoff’s first law)
In circuit inflow current's sum and outflow sum of done current same.
Inflow current – outflow current = 0
In this current flow below formula is formed in below circuit.
Written as a formula:
I1+I4 (INPUT CURRENT) = I2+I3+I5 (OUTPUT CURRENT)
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Kirchoff’s current
Law of Kirchoff’s current in circuit diagram.
In parallel circuit I = I1 + I2 + I3 = I4
I, I4 = Total current in circuit
I1 = consumption current of lamp1
I2 = consumption current of lamp2
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Kirchoff’s current law 2
1.11.2 Kirchoff’s voltage law (Kirchoff’s second law)
The source voltage of a series circuit is equal to the total value of each individual voltage
drop, and sum of voltage drop and sum of applied voltage big number are 0 (Zero).
Input source voltage – Sum of voltage drop = 0
1) When flow current in below circuit, voltage drop occurrence in resistance R1 and R2.
2) This voltage drop is proportional in resistance value of each resistance
Sum of voltage drop that is occurrence in each resistance is same with applied voltage.
Kirchoff’s voltage law 1
E1 = R1 x I (Volt) E2 = R2 x I(Volt)
E = E1 + E2 (Kirchoff’s voltage law) E = E1 + E2 = R1 I + R2 I = (R1 + R2) I
4) Kirchoff’s voltage law material for exercise.
Value of resistance R1 and R2 is different in this picture
Current is 4A and value of voltage drop is 8Volt
in resistance R1.
How many voltage drops from R2?
12Volt (power source) - 8Volt (R1 voltage
drop) = 4Volt
or
V2(R2 voltage drop) = 4A (total current) x R2
resistance
V1 = 2(R1) x 4(current I) = 8Volt
V2 = 1(R2) x 4(current I) = 4Volt Sum of
voltage drop = 8Volt + 4Volt = 12Volt (power source voltage)
Summary for Kirchoff’s law
If there is electric potential in a circuit, current passes and energy of electricity is converted
by machine energy or energy of light by this.
At this time, it is a kind of big resistance that produces energy and applied voltage or current
consumed all in resistance this operation resistance that energy of 100% emanates be.
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But, for example, if there is another big or small resistance behind or front of effector’s,
effectors does not get energy as much this resistance consumes current
Because voltage and current does not pass in effector’s as much consume in this
resistance does not get energy 100%.
1.12 Electromagnetism and Magnetic Circuit
1.12.1 Occurrence of Magnetic Force
The ancient Chinese navigators discovered that a small piece of odd stone, attached to a
string, would always turn in a northerly direction. These small stones were iron ore. The
Greeks called them magnetite because they were found near Magnesia in Asia Minor.
Since mariners used these stones in the navigation of their ships, the stones became
known as “leading stones”. These were the first forms of nature magnets. Today, a magnet
can be defined as a material or substance that has the power to attract iron steel and
magnetic materials.
1.12.2 Magnetic and Magnetic Forces
The greatest attractive force appeared at the ends of a magnetic. These concentrations of
magnetic force are called magnetic poles. Each magnet has a north pole and a south pole.
It was also discovered that many invisible lines of magnetic force existed between poles.
Each line of force was an independent line. None of the lines cross or touch a b d i li
Notice the pattern of lines existing between the poles. These lines of filings reflect the lines
of force. Note
the concentration of lines at each end of the magnet, or its poles. The lines of force are
more concentrated at the poles.
Each magnetic line of force travels forms the North Pole to the South Pole through space.
The line returns to the North Pole through the magnet itself.
These closed loops of the magnetic field can be described as magnetic circuits. Compare
the magnetic circuit to the electrical circuit. The magnetizing force can be compared to
voltage, and the magnetic lines of force can be compared to current.
When the North Pole of one magnet is close to the South Pole of the other, an attractive
force brings the two magnets together. If the magnets are turned so that two N poles or two
S poles are close to each other there is a repulsive force between the two magnets.
Figure 1. These figure show the magnetic field of attracting and repelling magnets.
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Further scientific investigation showed that the earth acts as one enormous magnet. The
earth’s magnetic poles are close to the north and south geographic poles. Refer to Figure
2.
Figure 2. The earth is a large magnetic, surrounded by a magnetic field.
You can observe that magnetic north and the north geographic pole do not coincide. A
compass would not necessarily point toward true north. This angle between true north and
magnetic north is called the angle of declination or declination or the angle of variation.
There is, however, a line around the earth where the angle of declination is zero. When
standing on this line, your compass would point to true north as well as magnetic north. At
all other locations on the surface of the earth, the compass reading must be corrected to
find true north.
What causes a substance to become magnetized? The molecules in and iron bar act as
tiny magnets.
Figure 3. Top-Molecules are not aligned. Bottom-Molecules have been aligned
If these tiny magnets are in a random order, Figure 3 (top), the bar does not act as a
magnet. However, when these tiny magnets are arranged so that their north and south
poles are in line, Figure 3 (bottom), the iron is magnetized.
This can be demonstrated by breaking a piece of magnetized iron into several pieces. Each
of the broken pieces acts as a separate magnet. Figure 4 shows a broken magnet. When
the iron is demagnetized, these molecules are placed back in random positions.
Figure 4. A long magnet may be broken into several smaller magnets.
This molecular action is further demonstrated by the way a magnet is made. For example,
take an unmagnified iron bar. Rub it a few times in the same direction with a permanent
magnet. A test (bring the bar near some iron filings) will show that the bar is now
magnetized.
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Figure 5. The nail is now magnetized.
Rubbing the iron bar with the magnet lines up the molecules and causes the iron to become
magnetized.
Permanent magnets are made by placing the material to be magnetized in a very strong
magnetic field.
Heat will destroy a magnet. Heat energy causes an increase in molecular activity and
expansion. This permits the molecules to return to their random positions on the
unmagnified piece of iron.
Figure 6. Heat will destroy a magnet.
Magnetic Flux
The many invisible lines of magnetic force surrounding a magnet are called the magnetic
flux. If a magnet is strong, these lines of flux will be denser. So, the field’s flux density, or
the number of lines per square inch or per square centimeter can determine the strength
of a magnetic field.
Magnetic Flux density = magnetic flux / area
B=Ø/A
where B equals flux density, Ø (the Greek letter phi) equals the number of lines, and A
equals the cross sectional area. The cross-sectional area can be measured in square
centimeters. If the cross-sectional area is measured in square centimeter, then the flux
density is given in the unit gauss. A gauss is the number of lines per square centimeter.
The flux, B, is usually given in Weber’s per square meter.
1.12.3 Electro Magnetic Induction
During the eighteenth and nineteenth centuries, a great deal of research was directed
toward discovering the link between electricity and magnetism. A Danish physicist, Hans
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Christian Oersted, discovered that a magnetic field existed around a conductor carrying an
electric current.
You can perform an experiment that shows the magnetic field around the current carrying
conductor. Pass a current carrying conductor through a sheet of cardboard. Placed small
compasses close to the conductor. The compasses will point in the direction of the
magnetic lines of force, Figure 7. Reversing the current will also reverse the direction of
the compasses by 180 degrees. This shows that the direction of the magnetic field depends
upon the direction of the current.
Figure 7. Compasses line up to show circular pattern of magnetic field around current
carrying conductor.
Magnetic field exists around a current-carrying conductor. In the conventional theory of
current direction, current is said to be from positive to negative. Using the right hand as
shown figure 8, with the thumb pointing in the direction of current, the fingers indicate the
direction of the magnetic field.
Figure 8. Demonstration of the right hand rule for conductors.
In Figure 9, the dot in the center of the conductor on the left as the point of an arrow. This
shows that current is flowing toward you. Circular arrows show the direction of the magnetic
field. This principle is very important when electrical wires carry alternating currents. This
is because the placement of wires, or lead dress, has an influence on the workings of a
circuit. Conductors are grouped in pairs whenever possible to eliminate heating effects and
radio interference caused by the magnetic field created by the current flow.
Figure 9. These conventions are used to show the link between current flow and the
magnetic field. The dot represents a current arrow heading toward you. The cross on the
right represents the tail end of the current arrow heading away from you.
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1.12.4 Solenoid
When a current-carrying conductor is would in the form of a coil, or solenoid, the
magnetic lines of force will be inside the coil and will be concentrated, making a stronger
magnetic field. A solenoid will appear as a magnetic field with a North Pole at one end,
and a South Pole at the opposite end. This solenoid is shown in Figure 10.
Figure 10. A wire wound into a coil is a solenoid and has polarity set by the direction of
current flow.
Figure 11. Magnetic field around coil Figure 12. Right hand rule for a coil
The polarity (direction) of these magnetic lines of force can be established by using the
right hand with the fingers pointing in the direction of current in the coil winding. The
thumb then points to the North Pole, Figure 12.
The strength of the magnetic field of a solenoid depends upon the number of turns of wire
in the coil and the size of the current in amperes flowing through the coil. The product of
the amperes and turns is called the ampere-turns (At or NI) of a coil. This is the unit of
measurement of field strength. If, for example, a coil of 500 ampere-turns will produce the
field strength required for some situation, any combination of turns and amperes totaling
500 will work.
Examples:
50 turns × 10 amps = 500At
100 turns × 5 amps = 500At
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1.12.5 Electromagnets
In the solenoid, air is the conductor of the magnetic field. Other substances conduct
magnetic lines of force better than air. These materials would be described as having
greater permeability.
Figure 13. The coil with an iron core is described as an electromagnet.
To demonstrate this, a soft iron core can be inserted in the solenoid coil, Figure 13. The
strength of the magnetic field is being greatly increased. There are two reasons for this
increase. First, the magnetic lines have been concentrated into the smaller cross-sectional
area of the core. Secondly, the iron provides a far better path (greater permeability) for the
magnetic lines. This device (solenoid with an iron core) is known as an electromagnet.
The rules used to learn the polarity of an electromagnet. The rules used to learn the polarity
of an electromagnet are the same as those for the solenoid. When an electromagnet is
energized it is a powerful magnet. When the electrical energy is disconnected the
electromagnet loses most of its magnetism, but not all of it. If the de-powered magnet is
brought near some iron filing, the filings will be attracted to the core because the iron core
has retained a small amount of its magnetism. This magnetism is called residual
magnetism.
If very little magnetism remains, the core would be considered, as having low receptivity
is the ability of a material to retain magnetism after the magnetizing field has been removed.
If a core retains a good deal of magnetism, it is said to have high receptivity. A soft iron
core shows low receptivity. A steel core has high receptivity.
EXERCISE:
1. A series-parallel electric circuit is illustrated below.
What is the potential difference across the terminal of resistor?
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2. A series-parallel electric is illustrated below.
What is the intensity of the current flowing from the power source, Is?
3. The following electric circuit consists of a power supply, five resistors (R1, R2, R3, R4
and R5) and an ammeter (A).
The ammeter reads 0.25 A.
a. What is the potential difference (voltage), Vt, across the terminals of the power supply?
b. What is the potential difference across R3?
c. What is the potential difference across R1?
d. What current flows through R5?
REFERENCE:
1. Hollembeak, B. (2015). Automotive electricy & electronics (6th ed.). New York:
Cengage.
2. Hollembeak, B. (2015). Shop manual for Automotive electricity & electronics (6th ed.).
USA: Cengage.
3. Halderman, J. (2014). Automotive Electricity and Electronics (Fourth edition.). Boston:
Pearson.
4. Halderman, J. D. (2013). Advanced Automotive Electricity and Electronics. Boston:
Pearson.
5. Chapman, N. (2010). Principles of Electricity & Electronics for the Automotive
Technician (Second edition.). Clifton Park: Delmar.
DPP C2(b)
Kolej Kemahiran Tinggi Mara
Masjid Tanah, Melaka
INFORMATION SHEET
PROGRAMME DIPLOMA IN AUTOMOTIVE ENGINEERING TECHNOLOGY
SESSION
CODE & COURSE SEMESTER 2
LECTURER
DVA 20212 ELECTRICAL & SHEET NO IS 07
ELECTRONIC FUNDAMENTAL
MOHD FARDZLEE BIN ABD PATAH WEEK 7
TOPIC 2.0 Tools & Test Equiptments
SUB-TOPIC 2.1 Basic equipments
2.2 Multimeters
TOPIC 2.3 Specialist equipment’s
LEARNING
OUTCOME After the lesson, student should be able to:
1. Explain voltmeter, ohmmeter, ammeter function and test light.
2. Identify specialist equipments.
Electrical Testers
The automotive technician must be familiar with several electrical testers in order to
troubleshoot electrical systems. Older electrical testers have a needle, or pointer, to
indicate the electrical reading. These testers are called analog gauges. Many modern
electrical testers are digital and display a number that indicates the electrical reading. Elec-
trical theory and the use of these testers will be covered in detail in later chapters.
2.1 Basic Equipments
Test Light
A test light is a simple electrical tester composed of a 12-volt light bulb, two terminals, and
connecting wiring. Using a test light is a quick way to check an electrical device or circuit.
However, test lights cannot be used to measure exact electrical units; they only indicate
whether electricity is present. A test light should not be used to check computers and other
solid-state devices because they can be ruined by the current flowing through the light.
There are two types of test lights. The powered test light contains a battery and is used to
check for a complete circuit when no current is flowing in the circuit, the non-powered test
light is connected between a powered circuit and ground. It will light up if power is present
in the circuit.
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Ohmmeter
Ohmmeters are used to measure electrical resistance. Resistance, which is
the opposition to current flow that exists in every electrical circuit or device,
is measured in Ohms. Ohmmeters can only check an electrical circuit when
no current is flowing in the circuit. An ohmmeter has two leads, which are
connected to each side of the unit or circuit to be tested. Polarity (direction
of current flow) is not important when checking resistance, except in the
case of diodes or some computer circuits. Most ohmmeters have selector
knobs for checking various ranges of resistance values. Analog ohmmeters
have a special knob to adjust the needle to zero before checking resistance.
Voltmeter
Voltmeters are used to check voltage, or electrical potential, between two
points in an energized circuit. The H circuit to be checked must have a
source of electricity available. On some voltmeters, different scales can be
selected, depending on the voltage level being measured. Always observe
proper polarity when attaching voltmeter leads. The negative lead should
always be connected to ground, and the positive lead should be attached
to the positive part of the circuit.
Ammeter
An ammeter is used to check the amperage (current) in a circuit. The
ammeter is used to check the amperage draw of starters or other motors
and to check battery condition. Ammeters can also be used to check the
amperage draw of ignition coils, solenoids and other electrical devices.
Tachometer
Tachometers are used to measure engine speed. Modern
tachometers are available in either analog or digital versions.
Tachometers have at least two leads. One lead is connected to the
distributor side of the ignition coil, and the other lead is connected
to ground. Some tachometers have a clamp-on pickup that is
placed around a plug wire to obtain the speed reading. The
tachometer may have a low range to set idle speeds and a high
range for making various tests at high engine speeds. The ranges
may be selected with a control knob, or they may switch automatically as engine speed
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varies. Some tachometers have a provision for checking distributor dwell, or the amount of
time that primary current is flowing in the ignition coil. This is useful when working on older
vehicles with point-type ignition systems.
2.2 Multimeter
Multimeters are meters that combine voltmeters, ammeters, ohmmeters, and other testers
into one unit. Multimeters usually have at least one positive lead (red) and one negative
lead (black). Some multimeters have additional leads for special functions. Polarity should
be carefully noted when making some tests with multimeters.
Analog Multimeter
Digital Multimeter
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2.3 Specialist Equipments
Oscilloscopes
An oscilloscope is a diagnostic tool that displays a line pattern, or
trace, representing circuit voltages in relation to time.
A scope is often used to check ignition system operating voltages.
It can also be used to check the output signals from sensors and
other electronic devices.
Engine analyzers
Consists basically of three parts.
Multimeter.
Gas analyser.
Oscilloscope.
Inductive pickups
An inductive pickup does NOT have to be touched to the metal
components in a circuit. It will sense the magnetic field around a current
carrying wire to make a measurement.
Insulation tester
It will check the plastic or rubber insulation on wires for deterioration
and leakage (current flowing out of insulation).
Inductive wire tracer
An inductive wire tracer can be used to find internal breaks in
wires and disconnected wires or terminals.
Load tester
A load tester is used to test batteries, the charging system,
and the starting system.
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Alternator bench tester
An alternator bench tester will check the output of an alternator off the
car.
IGNITION SYSTEM TEST EQUIPMENT
Specialized tools and equipment are also needed to service a car's ignition system.
Tach-dwell meter
A tach-dwell meter will measure engine speed, dwell (cam angle),
and sometimes resistance.
The tach or tachometer registers in RPM (revolutions per minute). It
is needed when adjusting engine speed settings and when doing
other tests
Photoelectric tachometer
A photoelectric tachometer can be used on diesels that do not have an
electrical ignition system. It will read light flashes from reflective tape
placed on the crankshaft damper.
Timing light
A timing light is a strobe light used to adjust ignition timing.
Electronic ignition analyzer
An electronic ignition analyzer will check the condition of several ignition
system components. Various designs are on the market and their
capabilities vary.
Magnetic timing meter
A magnetic timing meter is needed on some car engines with
provisions for a magnetic pickup.
sense engine speed and crankshaft position information
EXHAUST GAS ANALYZER
An exhaust gas analyzer will measure the chemical content in an
engine's exhaust.
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SCAN TOOLS (SCANNERS)
A scan tool, or scanner, is needed to check the operation of vehicle
sensors, actuators, wiring, and the computer itself.
HAND-HELD SCOPE
A hand-held scope usually consists of an oscilloscope and a multimeter
combined in one housing.
EXERCISE:
A multimeter is an electronic measuring instrument that combines several measurement
functions in one unit. A typical multimeter includes basic features such as the ability to
measure voltage, current, and resistance.
1. Use a multimeter to test the voltage on an assortment of batteries.
[Expected voltage is the voltage stamped on the battery.]
Set multimeter to The black lead goes in the COM port, the red lead is in the V port.
Battery Size
C size Expected Voltage Measured Voltage Good or Bad?
1.5 V 1.3 V Bad
2. Use your multimeter to measure the voltage of your 4-AA battery pack. What is the
voltage: _____________. These batteries are in series and their voltage is cumulative.
3. Use a multimeter to measure the resistance of the 3 resistors. After measuring the
value, verify that the resistor is within +- tolerance.
Set multimeter to The black lead goes in the COM port, the red lead is in the V port.
Resistor Band Colors Expected Measured
orange, orange, brown Resistance Percentage Resistance OK?
(read code)
328Ω
330Ω
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4. Voltage drop describes how the supplied energy of a voltage source is reduced as
electric current moves through the passive elements (elements that do not supply
voltage) of an electrical circuit.
Set multimeter to
Use your meter to measure the voltage drop across the LED and the voltage drop across
the 1000K resistor.
Battery Voltage = LED Voltage drop + Resistor Voltage drop
5. Now measure the current in the circuit using the multimeter (remove the LED). Then
compare your calculations above with the measurements below.
Resistor Current measured in the
value circuit
REFERENCE:
1. Hollembeak, B. (2015). Automotive electricy & electronics (6th ed.). New York:
Cengage.
2. Hollembeak, B. (2015). Shop manual for Automotive electricity & electronics (6th ed.).
USA: Cengage.
3. Halderman, J. (2014). Automotive Electricity and Electronics (Fourth edition.). Boston:
Pearson.
4. Halderman, J. D. (2013). Advanced Automotive Electricity and Electronics. Boston:
Pearson.
5. Chapman, N. (2010). Principles of Electricity & Electronics for the Automotive
Technician (Second edition.). Clifton Park: Delmar.
DPP C2(b)
Kolej Kemahiran Tinggi Mara
Masjid Tanah, Melaka
INFORMATION SHEET
PROGRAMME DIPLOMA IN AUTOMOTIVE ENGINEERING TECHNOLOGY
SESSION
CODE & COURSE SEMESTER 2
LECTURER
DVA 20212 ELECTRICAL & SHEET NO IS 8
ELECTRONIC FUNDAMENTAL
MOHD FARDZLEE BIN ABD PATAH WEEK 8
TOPIC 2.0 Tools & Test Equiptments
SUB-TOPIC 2.4. Inspection methods of components
2.5. Measure Voltage, Current and Resistance
TOPIC After the lesson, student should be able to:
LEARNING 1. Illustrate inspection methods of components.
OUTCOME 2. Identify type of inspection methods of components.
3. Discuss inspection methods of components.
2.4 Inspection Methods of Components
HOW TO CHECK CONNECTORS
The most common cause of connector problems are as follows:
1. Poor contact caused by pins coming out, which occurs when a pin is not pushed in all
the way.
2. Improper contact often occurs, because the male connector is not pushed in all the way
until it locks, the male pin is deformed, and so on.
3. Improper contact is sometimes caused by rust on the pins or water getting into the
connector.
CHECK FOR CONTACT RESISTANCE
Connect the connector to an ohmmeter as indicated below to
check for contact resistance.
Replace the connector if the meter reads 1 Q or more. If the
meter reads less than 1 Q, determine whether to replace the
connector depending on the load connected.
Examples:
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1. Headlight with 60-W low beam & 150-W high-beam: If the
meter reads 0.5 ohm, replace the connector.
2. Relay with 60-ohm coil: Relay okay -- do not replace.
CHECK FOR A VOLTAGE DROP
To check a connector for a voltage drop, connect the
connector with a meter as illustrated below, with the load in
operation. This check enables you to detect a faulty
connector that could not be detected in the contact
resistance check.
CHECK INSERTION FORCE
To check the insertion force of a connector, insert a male pin into
the mating female pin as illustrated below. If the pin goes in too
easily, it means that the spring of the female pin is weak, so the
female pin should be replaced.
HANDLING PRECAUTIONS
Almost all automotive connectors have lock mechanisms. Some connectors have a single
lock while others have a dual lock. Some locking mechanisms are released by being
pulled up and some by being pressed down.
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Most pins are provided with a locking mechanism that
prevents the pin from being pulled out of its connector when
the connectors are disconnected. Therefore, when
removing a pin from its connector, be sure to unlock it with
the proper tool. When inserting a pin, be sure the lock locks
the pins securely in place.
Hold the both connectors with both hands when disconnecting them.
Never pull on the wires.
Insert the male connector into the female connector until the lock
snaps and the connector cannot be pushed in any further.
SYSTEM INSPECTION METHODS
Trouble in electrical circuits may be pinpointed by one of the
following three methods:
a. By measuring the resistance of the individual electrical components;
b. By measuring the current flowing through the circuit;
c. By measuring the voltage drop(s).
The third method, measuring the voltage drop(s), is the most convenient method for
several reasons:
a. Before the resistance of the individual electrical components can be measured, the
b. components must be disconnected from the circuit,
c. Not all ohmmeters are accurate enough to correctly measure small resistance values
of only a few ohms.
d. An ammeter must be connected in series to measure the current flowing in the circuit.
This requires breaking the circuit.
e. Circuit trouble can therefore be most easily found by finding voltage drop values:
1. NORMAL CIRCUIT
The voltage drops across resistance R1 and R2 in the following circuit can be determined
as follows:
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Changes in potential at various points within the example circuit may be expressed as
follow:
2. BREAK IN CIRCUIT
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Assume, for example, that there is believed to be a break in the circuit at point (g) of
resistance R2 in the circuit below. To determine whether or not this is true, we can use a
voltmeter to measure the voltage drop between any point on the high side of the circuit
(for example, point © or (d) ) and the point (in this case, (g) ) where the open is assumed
to be.
If no voltage drop is found (that is, if the pointer of the voltmeter stays at 12 V), it means
that there is indeed an open in the circuit.
Changes in potential at various points in the above circuit may be expressed as follows:
3. SHORT CIRCUIT
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Let's assume there is suspected to be a short circuit at point(g) (the point that divides the
37 Q resistance of R3 from the 8 Q of R4) of resistance R2 (note that this, which is 45 Q, is
the total resistance obtained by adding R3 and R4) in the same circuit as above. Now, let's
check voltage drop V, across resistance R. From the above, we can conclude that voltage
drop vt across rt in this circuit is greater by 0.15 V than the value 0.75 V which was obtained
earlier.
Changes in potential at various points in the example circuit may be expressed as follows:
4. INCREASE IN TOTAL CIRCUIT RESISTANCE
Assuming the value of R2 in the following circuit has increased (from 45 Q to 57 Q) due to
damage, let's check voltage drop V, across R.
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Here, we can see that the voltage drops across R in this circuit is smaller by 0.15 V than
the value 0.75 V.
Changes in potential at various points within the example circuit may be expressed as
follows:
In conclusion, we can say the following three things:
a. By measuring the voltage drop across a resistance, we can find breaks in the circuit,
short circuits, and resistance that have changed.
b. If the voltage drop across a particular resistance is smaller than normal, it means
either that there is a short circuit in the resistance being measured, or that the
resistance value of another resistance in the same circuit has increased.
c. If the voltage drop across a particular resistance is greater than normal, it means
either that the resistance value of the resistance being measured has increased, or
that there is a short circuit in another resistance in the same circuit.
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2.5. Measure Voltage, Current and Resistance
How to Measure Voltage
1. Power off the circuity/wiring under test if there is a danger of shorting out closely spaced
adjacent wires, terminals or other points which have differing voltages.
2. Plug the black ground probe lead into the COM socket on the meter (see photo below).
3. Plug the red positive probe lead into the socket marked V (usually also marked with the
Greek letter "omega" Ω and possibly a diode symbol).
4. If the meter has a manual range setting dial, turn this to select AC or DC volts and pick
a range to give the required accuracy. So for instance measuring 12 volts on the 20
volt range will give more decimal places than on the 200 volt range.If the meter is auto
ranging, turn the dial to the 'V' setting with the symbol for AC or DC (see "What Do the
Symbols on the Range Dial Mean?" below).
5. A multimeter must be connected in parallel in a circuit (see diagram below) in order to
measure voltage. So this means the two test probes should be connected in parallel
with the voltage source, load or any other two points across which voltage needs to be
measured.
6. Touch the black probe against the first point of the circuitry/wiring.
7. Power up the equipment.
8. Touch the other red probe against the second point of test. Ensure you don't bridge the
gap between the point being tested and adjacent wiring, terminals or tracks on a PCB.
9. Take the reading on the LCD display.
Series and Parallel Connections
Measuring Voltage - Meter in Parallel with Load
DPP C2(b)
WARNING!!! Safety First When Measuring Mains Voltages!
1. Before using a meter to measure mains voltages, ensure the test leads aren't damaged
and that there are no exposed conductors which could be touched inadvertently.
2. Double check that the test leads are plugged into the common and voltage sockets of
the DMM (see photo below) and not the current sockets. This is essential to avoid
blowing up the meter.
3. Set the range dial on the meter to AC volts and the highest voltage range.
4. Always turn off the power (if possible) before inserting the probes into a socket outlet,
using the switch on the socket. Insert a probe into the neutral pin first before inserting a
probe into the hot (live) pin of the socket. If you insert the probe into the hot (live) pin
first and the meter is faulty, current could flow through the meter to the neutral probe. If
you then inadvertently touch the probe, there is a possibility of shock.
5. Finally turn on the power switch and measure the voltage.
Ideally buy and use a meter with a least CAT III or preferably CAT IV protection for
testing mains voltages. This type of meter will incorporate high rupturing capacity (HRC)
fuses and other internal safety components that offer the highest level of protection
against overloads and transients on the line being tested. A meter with less protection
can potentially blow up causing injury if it is connected incorrectly, or a transient voltage
generates an internal arc.
If you are measuring voltage at a consumer unit/breaker box/fuse box, this video from
Fluke Corporation outlines the precautions you should take
How to Measure Current
1. Turn off the power in the circuit being measured.
2. Connect the probe leads as shown in the photo below. Plug the black ground probe
lead into the COM socket.
3. Plug the red positive probe lead either into the mA socket or the high current socket
which is usually marked 10A (some meters have a 20 A socket instead of 10A). The mA
socket is often marked with the maximum current and if you estimate that the current
will be greater than this value, you must use the 10 A socket, otherwise you will end up
blowing a fuse in the meter.
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4. A multimeter must be inserted in series in a circuit in order to measure current. See the
diagram below.
5. Turn the dial on the meter to the highest current range (or the 10A range if the probe is
in the 10A socket). If the meter is auto ranging, set it to the "A" or mA setting. (See the
photo above for an explanation of symbols used).
6. Turn on the power.
7. If the range is too high, you can switch to a lower range to get a more accurate reading.
8. Remember to return the positive probe to the V socket when finished measuring current.
The meter is practically a short circuit when the lead is in the mA or 10 A socket. If you
forget and connect the meter to a voltage source when the lead is in this position, you
may end up blowing a fuse at best or blowing up the meter at worst! (On some meters
the 10A range is un-fused).
Connecting Probe Leads to Measure Current
Measuring Current - Meter in Series
Measuring Large Currents with a Clamp Meter (Tong Tester)
On most multimeters, the highest current range is 10 or 20 amps. It would be impractical
to feed very high currents through a meter because normal 4 mm sockets and test leads
wouldn't be capable of carrying high currents without overheating. Instead, clamp meters
are used for these measurements.
Clamp meters (as the name suggests), also known as tong testers, have a spring loaded
clamp like a giant clothes peg which clamps around a current carrying cable. The
advantage of this is that a circuit doesn't have to broke to insert a meter in series, and
power needn't be turned off as is the case when measuring current on a standard DMM.
Clamp meters use either an integrated current transformer or hall effect sensor to measure
the magnetic field produced by a flowing current. The meter can be a self-contained
instrument with an LCD which displays current, or alternatively the device can output a
voltage signal via probe leads and 4mm "banana" plugs to a standard DMM. The voltage
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is proportional to the measured signal, typically 1mv represents 1 amp. Clamp meters can
measure hundreds or thousands of amps.
To use a current clamp, you simply clamp over a single cable. In the case of a power cord
or multicore cable, you need to isolate one of the cores. If two cores carrying the same
current but in opposite directions are enclosed within the jaws (which would be the situation
if you clamp over a power cord), the magnetic fields due to the current flow would cancel
out and the reading would be zero.
How to Measure Resistance
1. If the component is on a circuit board or in an appliance, turn off the power
2. Disconnect one end of the component if it's in a circuit. This may involve pulling off
spade leads or desoldering. This is important as there may be other resistors or other
components having resistance, in parallel with the component being measured.
3. Connect the probes as shown in the photo below.
4. Turn the dial to the lowest Ohm or Ω range. This is likely to be the 200 ohm range or
similar.
5. Place a probe tip at each end of the component being measured.
6. If the display indicates "I", this means that resistance is greater than can be displayed
on the range setting you have selected, so you must turn the dial to the next highest
range. Repeat this until a value is displayed on the LCD.
7.
Connecting Probe Leads to Measure Resistance
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EXERCISE:
To test for a Voltage Drop on the Power side of a circuit, (figure 1) follow the steps below.
1) Connect the positive test lead of a Digital Volt/Ohm meter (DVOM) to the power source.
Use of an analog meter is not recommended because damage to the meter could result
from improper polarity.
2) Connect the negative test lead to the other end of the wire for the circuit being tested
(point A).
3) Operate the circuit and observe the meter voltage.
4) The DVM will display the difference in voltage between the two points.
To pin point, the component/connection responsible for the voltage drop, move the negative
test lead to the next component/connection (point B) in the circuit and retest at additional
points as necessary. Changes in the Voltage Drop Reading indicate where excessive
Voltage Drop is located.
To test for a Voltage Drop on the Ground side of a circuit, (figure 2) follow the steps below.
1) Connect the negative test lead of a Digital Volt/Ohm meter (DVOM) to the negative
battery terminal. Use of an analog meter is not recommended because damage to the
meter could result from improper polarity.
2) Connect the positive test lead to the ground terminal/wire at the unit being tested (point
A).
3) Operate the circuit and observe the meter voltage.
4) The DVM will display the difference in voltage between the two points.
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To pin point, the component/connection responsible for the voltage drop, move the negative
test lead to the next component/connection in the circuit and retest at additional points as
necessary. Changes in the Voltage Drop Reading indicate where excessive Voltage Drop
is located.
How Do You Check Voltage with a Multimeter?
How Do You Check if a Wire is Live with a Multimeter?
How Do You Check Voltage Drop with a Multimeter?
Why is Voltage Drop Important?
Can a wire carry a current and still be neutral—that is, have a total charge of zero?
Explain.
Car batteries are rated in ampere-hours (A⋅h). To what physical quantity do ampere-
hours correspond (voltage, charge, . . .), and what relationship do ampere-hours have
to energy content?
If two different wires having identical cross-sectional areas carry the same current, will
the drift velocity be higher or lower in the better conductor? Why are two conducting
paths from a voltage source to an electrical device needed to operate the device?
In cars, one battery terminal is connected to the metal body. How does this allow a
single wire to supply current to electrical devices rather than two wires?
Why isn’t a bird sitting on a high-voltage power line electrocuted? Contrast this with the
situation in which a large bird hits two wires simultaneously with its wings.
REFERENCE:
1. Hollembeak, B. (2015). Automotive electricy & electronics (6th ed.). New York:
Cengage.
2. Hollembeak, B. (2015). Shop manual for Automotive electricity & electronics (6th ed.).
USA: Cengage.
3. Halderman, J. (2014). Automotive Electricity and Electronics (Fourth edition.). Boston:
Pearson.
4. Halderman, J. D. (2013). Advanced Automotive Electricity and Electronics. Boston:
Pearson.
5. Chapman, N. (2010). Principles of Electricity & Electronics for the Automotive
Technician (Second edition.). Clifton Park: Delmar.
DPP C2(b)
Kolej Kemahiran Tinggi Mara
Masjid Tanah, Melaka
INFORMATION SHEET
PROGRAMME DIPLOMA IN AUTOMOTIVE ENGINEERING TECHNOLOGY
SESSION
CODE & COURSE SEMESTER 2
LECTURER
DVA 20212 ELECTRICAL & SHEET NO IS 09
ELECTRONIC FUNDAMENTAL
WEEK 9
TOPIC 2.0 Tools & Test Equiptments
2.6 Diagnostic procedures
SUB-TOPIC
TOPIC After the lesson, student should be able to:
LEARNING 1. Follow automotive electrical system diagnostic procedures.
OUTCOME
The ten-point diagnostic procedure relies on good communication, particularly from the
customer to the technician regarding what's going wrong with the automobile. A skilled
technician needs to have good "critical thinking" skills plus very good "problem solving"
skills. These skills are essential because modern vehicles with dozens of computers can
go wrong in an infinite number of ways.
Step One: The service writer interviews the customer and documents the symptoms on a
diagnostic form.
Step Two: The technician confirms the problem, and starts with some basic checks. For
example, check the battery and make sure the connections are in good condition.
Step Three: The technician then checks for any service updates related to the symptoms
and system with the problem. This is where a layperson may get the idea that "If you took
your BMW to a dealer this is what they do, they call the manufacturer and they say what to
repair." It's true that there are "pattern failures." Things can go wrong because of a faulty
batch of parts. These faults include related recalls and service updates. Once the
technician is sure there are not any quick fixes he is on his own!
Step Four: The skilled diagnostic technician, reviews the system being worked on and
starts a logical step by step diagnostic procedure.
Step Five: At this stage, the mechanic might call a technical support hotline, and go over
the process he is using. He might share data, and the support hot line might link with the
technician to work together to diagnose the problem in the most efficient way.
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Step Six: Once the problem has been diagnosed the technician reports his findings to the
service writer.
Step Seven: The service writer makes an estimate of what it will cost to complete the repair
and calls the customer to get approval to proceed. Sometimes we find a defective part, and
we have to replace it to continue the diagnosis. This could be the only problem or the first
step in the diagnosis.
Step Eight: Once the problem is repaired, the technician reassembles and tests the
vehicle. He saves the data in the computer. Sometimes we perform a complete electronic
scan of the car and save it in the computer.
Step Nine: The service writer then finishes documenting the repair.
Step Ten: Once everything has been documented, the vehicle is given a final test drive
and check before it is parked and is ready to be returned to the customer.
ELECTRICAL CIRCUIT CHECKS
All electrical circuits require voltage to operate the components connected to that circuit.
So if there is no voltage, there is no function. The first order of business when
troubleshooting electrical problems, therefore, is to check for the presence of voltage at the
load point in the circuit.
The load point is the element that the circuit is supposed to power, such as a light bulb,
wiper motor, blower motor, idle stop solenoid or whatever. And, all you need to quick check
it is a voltmeter or a 12-volt test light that glows when there is voltage. A voltmeter is the
best tool for this purpose because it will give you an exact reading, but a test light is OK for
performing quick voltage checks.
Using a test light is a quick way to check for voltage, but a voltmeter is more accurate.
Suppose you find no voltage at the load point. Ah ha, you have discovered your first clue
about the problem. Check the fuse, fuse link or circuit breaker that protects the circuit, or
the power relay that supplies voltage to the circuit.
If the problem is a blown fuse, replacing the fuse may restore power temporarily, but unless
the underlying cause for the overload is found and corrected, your "fix" probably will not
last. Whatever you do, do not substitute a fuse of greater capacity. A larger fuse may be
able to handle a greater load but the wiring and the rest of the circuit cannot. A circuit
designed for a 20-amp fuse is designed to handle a maximum of 20 amps. Period.
A faulty circuit breaker or an open relay will have the same effect as a blown fuse. Circuit
breakers are often used to protect circuits that may experience brief periods of overloading
such as an A/C compressor clutch.
The easiest way to check a circuit breaker is to bypass it with a jumper wire. Your jumper
wire should have a replaceable inline fuse to protect the circuit against damage. Use a fuse
of no greater capacity than what the circuit itself uses. If you do not know, use a 5- or 10-
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amp fuse to be safe. If the circuit works when you bypass the circuit breaker, you have
isolated the problem. Replace the circuit breaker.
This same basic test can also be used to check a questionable relay. A relay is nothing
more than a remote switch that uses an electromagnet to close a set of contact points.
When the relay magnet is supplied with voltage, the points close and battery voltage is
routed through the main circuit. Relays are often used in circuits to reduce the amount of
wiring that is required, and to reduce the current that flows through the primary control
switch. Thus, a relatively low amperage (make that cheap) switch, timer or sensor can be
used to turn a much higher capacity relay on and off.
VOLTAGE CHECKS FOR CAR ELECTRICAL PROBLEMS
Every electrical device also requires a certain amount of voltage to operate. A light bulb will
glow with reduced brilliance as the voltage drops. But for some components, there is a
threshold voltage below which it will not operate at all. A starter motor may crank the engine
more slowly with reduced voltage but, if the battery voltage is too low, it may not crank at
all. Minimum threshold voltage is especially critical for such components as solenoids
(which need a certain amount of voltage to overcome spring resistance), relays, timers,
buzzers, horns, fuel injectors (which are solenoids, too) and most electronics (the ignition
module, computer and radio).
Checking the load point for full battery voltage will tell you whether or not sufficient voltage
is getting through, and to do that you need a voltmeter. The battery itself should be at least
70 percent charged and read 12.43 volts or higher (12.66 volts is fully charged). If the
battery is low, it should be recharged and tested. The output of the charging system should
also be checked, and be about 1.5 to 2.0 volts higher than battery base voltage (around 14
to 14-1/2 volts). If the battery is OK, your voltmeter should read within 1 volt of battery
voltage at the circuit load point in any given circuit.
Low circuit voltage is usually caused by excessive resistance at some point in the wiring.
Usually this means a loose or corroded connector, a faulty switch or relay or poor ground.
To find the point of high resistance, use your voltmeter to do a "voltage drop test" at various
points throughout the circuit. If the voltmeter shows a drop of more than a 0.4 volts across
any connector, switch or ground contact, it means trouble. Ideally, the voltage drop should
be no more than 0.1 volts.
If low voltage is detected in a number of circuits, do a voltage drop test across the battery
terminals and engine/body ground straps. Loose or corroded battery cables and ground
straps are a common cause of voltage-related problems. Clean and tighten the battery
cables and/or ground straps, as needed.
Sometimes undersized wiring can cause low voltage. It is not something you will find in
many original equipment wiring circuits, but it is a common mistake that is made in many
do-it-yourself wiring installations for aftermarket accessories. The higher the amp load in
the circuit, the larger the required gauge size for the wiring. The following list includes
recommended wire gauge sizes:
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Wire size Amp Capacity
18 6
16 8
14 15
12 20
10 30
8 40
6 50
CONTINUITY
Every electrical circuit requires a complete circuit to operate. Voltage to the load will not do
any good unless there is also a complete ground path to the battery. The ground path in
the case of all metal-bodied cars is the body itself. In plastic-bodied cars, a separate ground
wire is needed to link the load to the chassis. In either case, a poor ground connection has
the same effect as an open switch. The circuit is not complete so current does not flow.
To check wiring continuity, you need an ohmmeter or a self-powered test light. An
ohmmeter is the better choice because it displays the exact amount of resistance between
any two test points. A test light, on the other hand, will glow when there is continuity but the
intensity of the bulb may vary depending on the amount of resistance in the circuit. But it is
OK for making quick checks.
Never use an ohmmeter to check resistance in a live circuit. Make sure there is no voltage
in the circuit by disconnecting it from its power source, by pulling the fuse or by testing
downstream from the circuit switch or relay. Ohmmeters cannot handle normal battery
voltage and, should you accidentally complete a circuit through the meter, you may damage
your meter.
Ohmmeters are great for measuring circuit resistance but you have to use care when
checking electronic components. An ohmmeter works by applying a small voltage through
its test leads, and this voltage can be enough to damage some electronic components
(such as the oxygen sensor). Special high impedance 10,000 mega-ohmmeters should be
used for electronics testing.
Tracing wires is not as easy as it looks because the circuit wire will sometimes change color
after passing through a connector, switch or relay. Always refer to a wiring diagram when
possible. This way you will know how the wires are routed and what colors are used.
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FINDING ELECTRICAL FAULTS
Now that we have covered some basic troubleshooting techniques, what is the best way to
find an electrical fault fast? It depends on the nature of the problem.
For a "dead" circuit, the first thing to look for is voltage at the load point. Use your voltmeter
or 12-volt test light to check for voltage. If there is voltage, the problem is either a bad
ground connection or the component itself has failed. Check the ground connection with
your ohmmeter. If the ground connection is good, the fault is inside the component. If there
is no voltage in the "hot" wire to the component, then the problem is in the wiring. Trace
back through the fuse panel (or relay or circuit breaker) until you find voltage. Now look for
an open or short that is preventing the current from reaching its correct destination.
Next comes bad connections. The resistance created by a loose or corroded connection
will cause a voltage drop that can have an adverse effect on circuit components. An
ohmmeter can be used to check non-powered circuit connections for excess resistance,
but a better method is to use a voltmeter to check for a voltage drop across a connection.
The voltmeter leads are connected on either side of the circuit component or connection
that is being tested. If a connection is loose or corroded, it will create resistance and
produce a reading on the voltmeter. As stated earlier, a voltage drop of more than 0.4 volts
means trouble, and ideally it should be 0.1 volts or less.
The worst kind of electrical problem to troubleshoot is an intermittent one. Everything works
fine in the shop but as soon as the customer gets the car back it starts to act up again. An
intermittent open or short is usually the result of something heating up and breaking (or
making) contact, or something that is loose and is making periodic contact.
Loose or corroded connections and switches are often responsible for this kind of problem,
so try jiggling the wires and circuit switch to see if it changes circuit voltage or resistance.
A wire that is rubbing and has chaffed away some of its insulation can make intermittent
contact causing a short, so again wiggling suspicious wires will often reveal the problem.
Temperature-sensitive intermittent shorts or opens can be the hard to identify because you
frequently have to simulate the exact circumstances that cause them to happen.
Sometimes you can assume what is happening by the nature of the problem. But it is
always more satisfying (and assuring) to duplicate the problem so you know for sure what
is wrong.
When does the problem occur? Does it only happen when the engine is hot or after the
circuit has been on for a period of time? Using a hot air gun or hair dryer to heat wires,
connectors, switches and relays can sometimes help identify troublesome components.
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Environmental factors often play havoc with electrical systems, too. Road splash or water
leaking through a crack in the cowl, under the windshield or around a grommet can
sometimes short out a circuit. Look for obvious signs of corrosion or leakage, and if you
find none check the condition of nearby weather seals.
A final note on repairing electrical faults: When splicing wires do not just twist them together
and wrap electrical tape around the connection. Use a solderless crimp-on connector, or
twist the wires together, solder them and use shrink wrap electrical insulation tubing to seal
the repair.
EXERCISE:
Symptoms
Here are some of the signs that indicate a probable electrical system issue with a car.
It doesn't start.
You hear a clicking sound but the car doesn't start.
Headlights tend to be dim.
Battery light comes on.
State the solving procedures.
REFERENCE:
1. Hollembeak, B. (2015). Automotive electricy & electronics (6th ed.). New York:
Cengage.
2. Hollembeak, B. (2015). Shop manual for Automotive electricity & electronics (6th ed.).
USA: Cengage.
3. Halderman, J. (2014). Automotive Electricity and Electronics (Fourth edition.). Boston:
Pearson.
4. Halderman, J. D. (2013). Advanced Automotive Electricity and Electronics. Boston:
Pearson.
5. Chapman, N. (2010). Principles of Electricity & Electronics for the Automotive
Technician (Second edition.). Clifton Park: Delmar.
DPP C2(b)
Kolej Kemahiran Tinggi Mara
Masjid Tanah, Melaka
INFORMATION SHEET
PROGRAMME DIPLOMA IN AUTOMOTIVE ENGINEERING TECHNOLOGY
SESSION
CODE & COURSE SEMESTER 2
LECTURER
DVA 20212 ELECTRICAL & SHEET NO IS 10
ELECTRONIC FUNDAMENTAL
WEEK 10
TOPIC 3.0 Automotive Electrical System
SUB-TOPIC 3.1 Electrical Wire, Terminals, Relays, Solenoid and Switching
3.2 Wiring diagram, symbols and wire colour coding
TOPIC After the lesson, student should be able to:
LEARNING 1. Define automotive electrical system.
OUTCOME 2. Identify electrical wire, terminals, connectors, relays, solenoid
and switches.
Types of Automotive Wires You Need to Know About
Automotive wires are special wires used to connect various 12V electrical accessories in
automobiles. Some of these accessories include automotive relays, switch panels, and fuse
blocks. Automotive wires are categorized into cross-linked and PVC wires, depending on
the type of insulation materials used during their manufacturing. Let’s take a look at
the various types of automotive wires used in the automobile industry.
Brief Introduction to PVC and Cross-Linked Insulation
The following explanations will give a brief idea of PVC and cross-linked insulation wires.
PVC: This term is used for cables that have polyvinyl chloride insulation. The PVC
is heated and extruded through a die on strands.
Cross-Linked: This term is used for cables that are cross-linked under heat and
pressure for better insulation properties. The material is subjected to heat and
pressure, and is extruded through the tube. These wires can withstand higher
temperatures than PVC wires.
Understanding Various Types of Automotive Wires
This section discusses various types of wires used in automobiles such as car, RV,
motorcycle applications, etc. These industrial wires are made to resist temperature, heat,
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vibration, and chemicals. Following are some of the popular types of automotive wires in
use.
Type GPT Wires, or Primary Wires: These are the most common types of wires
available for purchase in automotive stores. These wires have multi-stranded cores
with flexible insulation, which makes them perfect for tight spaces. These wires have
a temperature range of -40 o C to 80°C. Also, some wires have a high rating of 105
°C. These wires can easily resist chemicals, oils, and acids. Conductor: Bare
Copper; Insulation: Polyvinylchloride (PVC);
Type TWP (Thin Wall Thermoplastic) Wires: These are used in automotive
applications that require wires with minimal weight and small diameters. These wires
are rated in the temperature range of -40°C to 105°C. Conductor: Bare Copper;
Insulation: Polyvinylchloride (PVC)
Type HDT (Heavy Duty Thermoplastic) Wires: These wires are designed for
complex automotive applications that require protection from external threats. These
cables are employed for surface wiring in a variety of vehicles including RVs, buses,
trucks, etc. These wires have a recommended temperature range of 40 o C to
80°C. Conductor: Stranded Bare Copper; Insulation: Polyvinylchloride
(PVC); Voltage rating: 60 Volts
Type GXL Wires: These are thin wall XLP wires, primarily used in engine
compartments, which require high heat resistance. The recommended temperature
range of these wires is -51°C to 125°C. These wires have thinner walls, which makes
them easy for tight spaces. Conductor: Bare Copper; Insulation: Thin Wall Cross-
Linked Polyethylene (XLPE)
Type SXL Wires: These wires can withstand high heat, aging, and abrasion. These
wires are preferred for high-stress applications such as industrial use vehicles.
These wires have a temperature range of -51°C to +125°C. Conductor: Bare
Copper; Insulation: Thin Wall Cross-Linked Polyethylene (XLPE); Voltage rating:
50 volts
Type TXL Wires: These wires have extra thin walls, and are suited for automotive
applications that require minimal weight and size. These wires have a recommended
temperature range of -51°C to +125°C. Conductor: Bare Copper; Insulation:
Cross-Linked Polyethylene (XLPE); Voltage rating: 50 volts
Other Types of Automotive Wires
Following are some of the other important types of wires used in automotive applications.
Motor Wires: These wires have fine strands of conductor material, and can
withstand high voltages. These wires have a temperature rating of 221ºF (105ºC)
and voltage rating of 600 volts. Motor wires can resist oil, grease, water, solvents,
and fungus.
Battery Cables: These cables have a high wire gauge, and are used to connect a
battery to a car’s electrical system. These cables are susceptible to corrosion. As a
preliminary measure, every vehicle owner is recommended to check their battery
cables, if they face a starting issue.
Speaker Wires: These wires are used for audio applications. These wires are made
for low voltage use, and are not recommended for heavy load applications.
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Today, many automotive wire manufacturers provide automotive primary wire
customization services. They may add three stripes called tracers for easy identification of
cable jackets. Also, they can print logos, texts, or numbers over wire jackets. Many other
value added services such as twisting, paralleling, or cut-and-strip are also provided. These
customized automotive wires allow automotive manufacturers to maintain uniqueness
throughout their production processes. The customized cables are easy to identify, install,
and help save confusions during assembly.
Understanding Automotive Wire Harnesses and Their Applications
Introduction to Automotive Wire Harnesses
A wire harness is defined as an assembly of electrical cables, which is used to transmit
signals in various electrical applications. Automotive wire harnesses combine wiring of
different electrical as well as electronic devices in a single system. In short, wiring
harnesses are used in automobiles for transmission of signals, and powers different
electronic and electrical devices.
Industrial Applications of Wire Harnesses for Automobiles
Wire harnesses are used to set up electrical circuits in automobiles. They are used in cars,
two wheelers, three wheelers, commercial vehicles, and utility vehicles. These harnesses
are embedded in some of the following applications:
Body Harnesses: These include dashboards, power windows, door locks, and all
interior electrical components.
Chassis Wiring: These comprise rear, front, and main harnesses.
Engine Harnesses: These include fuel injection systems, speed sensors, and
cruise control systems, and lock braking systems.
Benefits of Automotive Wire Harnesses
Automotive wire harnesses provide several benefits, when compared to regular loose
cables and wires, such as:
Reduced Risk of Shorting: The wires are constricted into non-flexing bundles,
which minimizes the risk of shorting in electrical circuits.
Reduces Installation Time: The installation time for wire harnesses is significantly
less when compared to loose wires. This also lowers the risk of fires caused by
incorrect wiring.
Made for Harsh Environments: The automotive wiring harnesses are made from
durable materials, which make the wires ductile and durable. These harnesses can
perform under harsh conditions, and can carry heavy power loads.
Easy Customization: The wire harnesses used in automobiles can be easily
customized to meet client specifications and requirements, such as specific color
coding, high power transmission, etc.
Valuable Contributions in Hybrid Cars: There is a high demand for hybrid cars
that can provide optimum performance in harsh environmental conditions. In such
cars, wiring and cable harnesses are used to transmit high currents in extreme
conditions. These harnesses can handle electrical loads, resist electromagnetic
noise, and high heat.
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Environment-friendly: Wiring harnesses are environment-friendly because they
play a major role in improving the fuel efficiency of any automobile.
Crimp-Style Connections
This connection is simple to master, but before I show you the fundamentals of the
connection itself, let’s talk first about the different types of crimp connectors available.
Crimp connectors are available in sizes to accommodate up to the largest gauge of wiring,
including the really big stuff.
Seam versus Seamless Connectors
Although they may look similar from the outside, they are absolutely not. Quite simply,
seamless crimp connectors are cut from round stock so they are tube-like in nature.
Cheaper seam-type connectors are cut from flat stock and rolled into a tube-like shape, so
they have a seam that runs the length of the connection. This can be hard to see through
the insulation of the connector, but you can typically look at the ends to tell which type of
connector you have.
On the right, I removed some of the insulation from the connector. A quick look to determine
what kind of connector you’re crimping ensures that you crimp it properly.
Yes, I think this is a lousy crimp tool. But, if this is all you have to use, it’s even more
important to orient the connector in the tool correctly.
DPP C2(b)
This is the right tool for a crimping job. Notice the seam is opposite the stake to prevent the
stake from opening up the connector in the process of crimping, resulting in a questionable
connection.
This is especially important to know before you crimp the connector.
I typically only use seamless connectors for this very reason, but if you’re crimping a
seamed connector, be sure to crimp it in such a way that the seam isn’t opened up in the
process. This is easily accomplished by verifying the seam is perpendicular to the tool and
opposite the stake if you’re using a staking-type crimp tool.
Non-Insulated Connectors
Obviously, this type of connector has no insulation on it so it must be properly insulated
after you’ve crimped it in place—typically with heat shrink tubing. These types of connectors
are available in a wide variety—from butt connectors to ring terminals, seam or seamless.
The proper crimp tool for this type of connector is a staking-type crimp tool.
Either of these tools is suitable to properly crimp non-insulated connectors. I don’t purchase
non-insulated connectors, as one can simply remove the insulation from any insulated
connector and have a non-insulated connector, should the need arise.
Insulated Connectors
This is the most common of all mechanical connectors. Like their non-insulated cousin,
these are widely available in all different types and sizes and can also be seam or seamless
type. They can have vinyl or nylon insulation on them, and this insulation can be straight or
flared at the ends. The trick here is to pick the connector that properly fits both the gauge
and the insulation OD of the wire you are crimping it onto.
DPP C2(b)
Insulated connectors are my connector of choice because it saves time when you don’t
have to insulate the connector after the crimping has been done. I have many different
types of these on hand to accommodate any crimping job that I may come across.
Notice how the plastic insulation of the 8 AWG wire itself fits nicely into the insulation around
this crimp connector. Some connectors have flared ends (such as this one), while others
do not. I find that flared end connectors offer a higher likelihood of a perfect fit. This is
equally as important as the wire fitting into the ferrule itself.
Heat Shrinkable Insulated Connectors
These are the nicest of all crimp connectors. Use them one time, and it’s hard to go back
to anything else. But, they’re very expensive. The mechanics of using them are identical to
typical insulated connectors, but the insulation is heat shrinkable to provide a weather-tight
connection—perfect for under the hood, underneath the vehicle, or even marine use! Just
crimp, and heat for a long-lasting waterproof connection.
These connectors provide an exceptional connection and insulation. Think of them as a
combination of a crimp connector with a heat shrinkable insulation surrounding them.
Some, such as the 3M ones pictured, even have glue in them to provide a waterproof
connection!
DPP C2(b)
Look closely at the glue at each end. These connectors are suited for even the most
arduous environments. The glue helps to encapsulate the electrical connection and protect
it from the elements.
Different Kinds of Crimp Connectors
One of the reasons that crimp connectors are so popular is the variety of connectors that
are readily available. In addition, they’re relatively inexpensive. This makes it easy to have
a good selection of them on hand—I buy them in bulk so that I never run out. In addition, I
like to “stock” all the various sizes available so that I always have what I need for the task
at hand. I prefer insulated connectors over no insulated.
Butt Connectors: These are for making butt, or end-to-end, connections between two wires.
This is one of the most common crimp connections, and these are readily available up to 8
AWG, with even larger sizes available on request.
Ring Terminals: The ring terminal is the second most common crimp connector. These are
quite handy for terminating a wire to a connection point, such as a stud or bolt on the rear
of a typical alternator. They’re also used extensively to terminate a wire to a ground point.
These are readily available with all different diameter rings and as large as wire is available.
Fork Terminals (Spade Terminals): These are popular because they allow termination of a
wire to a connection point and provide easy connection to said point. A ring terminal
requires that you totally remove the nut from the bolt or stud you’re connecting to in order
to establish the connection. A fork terminal allows you to simply loosen said bolt or stud
and slide the terminal underneath. This is especially valuable when connecting to a barrier
strip with multiple connections. These are readily available based on the diameter of the
bolt that they need to fit around. I’ve been known to modify a ring into a fork on occasion!
Quick Disconnect Connectors: I use these a lot because I try my best to keep serviceability
in mind when adding a circuit to any vehicle. I use these wherever I need a simple
DPP C2(b)
connection to be easily disconnected. A good example is when mounting a switch or light
in a dash panel that is removable. When removing the panel, a quick disconnect connection
on the switch or light allows the panel to be quickly removed. This pays off in spades if your
dealer services your vehicle, and they need to remove said panel. Instead of cutting your
wiring, they simply unplug it.
A ring modified into a fork terminal. Simple and easy, this can be a real life saver if you
don’t have a fork large enough for the job at hand.
The dash of my Mustang has two LEDs that monitor the operation of the installed
water/methanol injection system. As they are mounted into the trim piece surrounding the
cluster, quick disconnects allow a simple removal.
Quick disconnects are readily available for wire and cables of all sizes. I prefer the fully
insulated push-on connector style over the bullet style.
DPP C2(b)
Filling the body of a quick disconnect with lithium grease is always a great idea with using
these connectors under the hood or under the vehicle.
There are two types: bullet connectors and push-on connectors. Obviously, they’re both
available in male and female versions.
The push-on type makes a really good connection. I typically use this style of connector
rather than a plug-type connector when dealing with fewer than four wires. With four or
more wires, a male and female plug is really the correct way to do things. This connector
is suitable for low-current use under the hood or vehicle as well. If you use them in this
environment, I recommend that you fill them with white lithium grease before pushing them
together. This helps keep the elements from affecting the electrical connection.
Relays
Relays feature two basic circuits: one circuit turns the relay on and off, and the other circuit
passes current through the relay once the relay is turned on. A relay acts like a switch. It
turns power on and off on demand and serves as an isolator, preventing the high power
demands of certain accessories from damaging other circuits that aren’t designed to handle
heavy loads. Placing a relay in the circuit allows the actual control switch to experience only
a small level of the power running through the circuit. Basically, a relay is a heavy-duty
switch that’s activated by the primary control switch. Relays in the 30 amp range are
required for accessories such as auxiliary driving lights, audio system amplifiers, electric
fans, electric fuel pumps, electric water pumps, etc.
Always install a dedicated relay with each applicable circuit (don’t assume that a single
relay can handle multiple circuits). The relay handles the heavy amperage in the circuit,
allowing the control switch to simply turn the relay on and off. A relay also can help to boost
a signal in a long wire run. For example, when a wire runs from the battery to the switch
and from the switch to the accessory, a lengthy wire can reduce the power available at the
accessory. A relay can be positioned to shorten the length of the power circuit, maximizing
power available to the accessory motor.
Solenoid
Solenoid is a coil of insulated or enamelled wire wound on a rod-shaped form made of solid
iron, solid steel, or powdered iron. Devices of this kind can be used as electromagnets, as
inductors in electronic circuits, and as miniature wireless receiving antennas.
DPP C2(b)
In a solenoid, the core material is ferromagnetic, meaning that it concentrates magnetic
lines of flux. This increases the inductance of the coil far beyond the inductance obtainable
with an air-core coil of the same dimensions and the same number of turns.
When current flows in the coil, most of the resulting magnetic flux exists within the core
material. Some flux appears outside the coil near the ends of the core; a small amount of
flux also appears outside the coil and off to the side.
A solenoid chime is wound on a cylindrical, hollow, plastic or phenolic form with a movable,
solid iron or steel core. The core can travel in and out of the coil along its axis. The coil is
oriented vertically; the core normally rests somewhat below the coil center. When a current
pulse is applied to the coil, the magnetic field pulls the core forcefully upward. Inertia carries
the core above the center of the coil, where the core strikes a piece of metal similar to a
xylophone bell, causing a loud "ding".
Types of Electrical Switches
Switch function is defined by the number of poles and throws the switch has. “Poles” are
individual circuits the switch controls (e.g., a “3-pole” switch has three circuits controlled by
the same throw). “Throws” are unique positions or settings for the switch (e.g., a “double-
throw switch” can operate in two different positions like on/off, high/low, etc.). Combining
the number of poles and throws gives a succinct description of the switch’s function, so the
function of, for instance, a “single-pole, double-throw” switch is implicit. Switch types are
commonly abbreviated for brevity, so a single-pole, double-throw switch would be referred
to as an “SPDT” switch.
The simplest type of switch is a single-pole, single-throw (SPST) device that functions as
an on-off switch. Double-pole, double-throw (DPDT) switches are commonly employed as
internal polarity reversing circuits. Switches of up to four poles and three throws are
common and some have breaks.
Foot Switches
Foot Switches are electro-mechanical devices used to control
power in an electrical circuit by foot pressure. They are often
used on machines where an operator needs his or her hands
to stabilize a work piece.
Key specifications include number of pedals, switching
function, voltage rating, and current rating.
Foot switches find use in many press applications where hand
controls cannot be used to actuate a cycle. They are also
commonly used in hospital equipment and office machines.
DPP C2(b)
Level Switches
Level Switches are electro-mechanical devices used to detect
the level of liquids, powders, or solids. They are mounted in
tanks, hoppers, or bins, and can provide output to a control
system. In some instances, they can be used to actuate a
device directly, such as level switches used in residential sump
pumps.
Key specifications include measured media, output type,
switch type, voltage and current ratings, and the materials
used for the body, stem, and float.
Level switches are used extensively in the process industries
to monitor tank and hopper levels. They are used in everyday
applications as well.
Limit Switches
Limit Switches are electro-mechanical devices designed to
sense motion and position mechanically and provide output
signals to a controller. They are available as bare switches, or
in rugged enclosures intended for the tough environment of a
factory floor.
Key specifications include actuator type, voltage, and current
ratings. A variety of actuator types from rods to whiskers
ensures that any manner of machine, component, or work
pieces can be sensed by a limit switch.
Limit switches are used in many common consumer machines
such as washing machines. In their ruggedized form they are
used in many types of manufacturing facilities such as steel
mills and paper plants.
Membrane Switches
Membrane Switches are circuit board based electro-mechanical
devices that provide tactile control of processes and machines
without the need for individual push switches. They are often custom
designed to suit a particular process.
Key specifications include circuit assembly type, actuator type, and
terminal type. Number of keys, graphics, illumination, and displays
can also be important features.
Membrane Switches are common in commercial products where
incorporating all control functions into a single device can save costs
over using discrete switches.
Pressure Switches
Pressure Switches are electro-mechanical devices used to sense fluid pressure and
provide output signals to a controller. They often employ a diaphragm as the sensing
means.
DPP C2(b)
Key specifications include the pressure type, media measured,
diaphragm material, pressure connection, minimum and
maximum working pressures, and maximum switch current.
Pressure switches are used to keep pressure within limits in
lubrication systems where over-pressure or under-pressure
conditions can result in damage to the machine.
Pull Chain Switches
Pull Chain Switches are electro-
mechanical devices that are hand
operated and used to switch a
circuit on and off, or step a circuit
through increasing power levels. Their most common
application is in lighting where they are used to switch lamps.
Pull Rope Switches are used as emergency stop devices.
Key specifications include switching function, voltage and
current ratings, as well as various features specific to e-stop
applications such as broken-cable detection.
Pull chain switches can be used for manual control of
overhead lights and fans. As rope-pull switches, they are used for emergency stop devices,
for example along the length of an in-running roll. They are sometimes called Rope Pulls
or Cable Pulls.
Pushbutton Switches Pushbutton Switches, also referred to as Push Switches, are
scenarios. hand operated electro-mechanical devices used for switching
circuits. They are the most common variety of switch used on
industrial control panels.
Key specifications include single-throw or double-throw
switching function, contact type, mounting type, actuator type,
and panel cut-out diameter. The 30 mm cut-out is a common
industrial size.
Pushbutton switches make up the bulk of manual switches
used in industrial controls. They are available in a variety of
shapes and styles to cover almost any manual control
DPP C2(b)
Rocker Switches
Rocker Switches are hand operated electro-mechanical devices used
for switching circuits. The switch operator position, raised or
depressed, gives a quick visual indication of the circuit's on or off
status.
Key specifications include single-throw or double-throw switching
function, mounting type, actuator type, and panel cut-out dimensions.
Rocker switches are used for manual switching in many industrial
controls as well as for control of consumer goods and office machines.
Rotary Switches Rotary Switches are hand operated electro-mechanical
Paddle Switches. devices used for switching circuits and selecting functions.
Rotary switches can be two-position, on-off, or they can have
multiple discrete stops.
Key specifications include number of poles, number of
positions, construction type, mounting type, and panel cut-out
diameter for panel mount switches.
Rotary switches are used to provide a visually verifiable means
of switch position, allowing operators to tell with a glance
whether a circuit is energized or not. They are also called
Slide Switches
Slide Switches are hand operated electro-mechanical devices used for switching circuits.
The switch operator is in the form of a slider that moves from position to position to control
the circuit status. Key specifications include single-throw or double-throw switching
function, mounting type, and panel cut-out dimensions.
Slide switches are used in electrical and electronic equipment where the switching range
can be limited and economy is important. They are commonly used for on-off buttons or
just as a general control switch.
DPP C2(b)
Thumbwheel / Pushwheel Switches
Thumbwheel Switches, also referred to as Pushwheel
Switches, are hand operated electro-mechanical devices used
to control electrical circuits with a rotatable wheel. They display
a numeric value corresponding to the switch position.
Key specifications include number of positions, mounting type,
actuator type, coded output type, and panel cut-out
dimensions.
Thumbwheel switches are widely used in the aviation industry
for flight controls, instrumentation, and controllers. They are
also used in test and measurement equipment and computer
devices.
Toggle Switches
Toggle Switches are hand operated electro-mechanical devices
used for switching circuits. They are actuated by a lever which is
pushed through a small arc. Moving the lever back and forth
opens and closes an electrical circuit, while the lever position
gives a quick visualization of the circuit status.
Key specifications include single-throw or double-throw switching
function, 1-axis, 2-axis, or 3-axis configuration, or in some cases
omnidirectional or joystick toggle configuration, and actuator type.
Toggle switched are used extensively in electronics panels and
instrumentation where a wider range of switching function is required, such as in
switchboards.
What is a Wiring Diagram?
A wiring diagram is a simple visual representation of the physical connections and physical
layout of an electrical system or circuit. It shows how the electrical wires are interconnected
and can also show where fixtures and components may be connected to the system.
When and How to Use a Wiring Diagram
Use wiring diagrams to assist in building or manufacturing the circuit or electronic device.
They are also useful for making repairs. DIY enthusiasts use wiring diagrams but they are
also common in home building and auto repair. For example, a home builder will want to
confirm the physical location of electrical outlets and light fixtures using a wiring diagram to
avoid costly mistakes and building code violations.
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