Troubleshooting package-type air-conditioning units(PACU) / commercial refrigeration equipment (CRE)

Job Sheet

3. Test the terminal of each circuit to
determine which circuit is shorted.

If short comes from the evaporator
fan motor circuit:

a. Check capacitors condition
b. Check evaporator fan motor

winding
c. Check solenoid valve (if

available)
d. Check electrical wiring

(sometimes when electrical
wiring rubs together, insulator
sometimes break which
makes electrical short in the
system)

If short comes from the compressor
motor circuit:

a. Check compressor motor
winding

b. Check capacitors condition (if
capacitor is available)

c. Check potential relay’s
condition (if potential relay is
available)

d. Check electrical wiring
(sometimes when electrical
wiring rubs together, insulator
sometimes break which
makes electrical short in the
system)

If short comes from the evaporator
fan motor circuit:

a. Check capacitors condition
b. Check condenser fan motor

winding
c. Check solenoid valve (if

available)
d. Check electrical wiring

(sometimes when electrical
wiring rubs together, insulator
sometimes break which
makes electrical short in the
system)

Job Sheet

4. Once trouble has been found,
corrective action should be made.

5. After troubleshooting the unit,
prepare report and submit it to your
instructor.

6. Clean your work area and store tools
and equipment used.

Evaluation:

While performing the activity it is important for you to assess your performance
following the criteria below:

 Circuit isolation is implemented in troubleshooting
 Source of electrical short is pinpointed
 Defective components and devices are repaired/replaced
 Safety and proper housekeeping is employed during the activity.

Trouble shooting of PACU/CRE

LOI Plan and prepare for trouble shooting

Introduction:
To troubleshoot and service PACU/CR properly the technician must

posses the following.

 A thorough understanding of the theory of refrigeration.
 A good working knowledge of the purpose, design and operation

of the various mechanical ad electrical parts of PACU/CRE.
 The ability to diagnose and correct any trouble that may develop.

On the initial contact, always allow the customer to explain the
problem, many times the trouble can be diagnosed through the customer’s
explanation. It is not right to jump to conclusion not until you have evaluated the
given information from the owner. After obtaining it, proceed with your trouble
shooting analysis.

Prepare all your needed tools and equipment and make visual
inspection and operation check of the unit to determine the following:

 Is the unit properly installed?
 Is the condenser located with proper dissipation of heat? Check

recommended spacing from rear wall and clearance above cabinet.
 Feel the condenser. With the compressor in the operation, the

condenser should be hot, with the gradual reduction in the
temperature from the top the to the bottom of the condenser.
 Are door gaskets sealing on pilaster area?
 Does the door, for provisions compartment and freezer
compartment actuate the light switch?
 Is freezer compartment fair guard in place?
 Is freezer compartment fan properly located on motor shaft?
 Is the thermostat thermal element properly installed?
 Observed the frost pattern on the evaporator.
 Check the thermos knob setting.
 Check the air-damper control knob setting.
 Inscribed bracket opposite slotted shaft of defrost timer to
determine if timer advances.
 Is condenser fan operating? It should operate when compressor
operates.
 Are air supplies free from obstructions?

The service technician should inquire regarding the number of
people in the family or number of customer the comes in and out of the building.
This will help determined the service load and daily door opening. In addition he
should know the room or compartment temperature.

After this phase of diagnosis is completed a through operational
check should be made on the refrigeration system. Any components not
previously checked must be checked properly.

Self Check
True or False: Read the statement carefully. Write true on the space provided if
the statement is correct and false if the statement is incorrect.

1. To troubleshoot a PACU/CRE system a technician should
have a thorough understanding of the theory of refrigeration.

2. The technician should have the ability to diagnose and
correct many troubles that may develop.

3. During visual inspection and operational check up
determined if the unit is properly installed.

4. He should also determine the location of the condenser with
proper dissipation of heat.

5. He should see to it that the air supply is free from
obstruction.

Answers.
1. True
2. True
3. True
4. True
5. True

Troubleshooting PACU/CRE

LO2

Introduction:
Electric motor problems are either mechanical or electrical.

Mechanical problems may sometimes appear to be electrical. For example, a
bearing dragging in a small permanent split capacitated fan motor may not make
any noise. The motor may not start, and it appears to be an electrical problem.
The technician must know how to correctly diagnose the problem.. This is
particularly true with open motors, because if the driven component is stocked, a
motor maybe changed unnecessarily. If the stock component is a hermetic
compressor, the whole compressor must be changed ; if it is serviceable
hermetic compressor, the motor can be replaced or the compressor running gear
can be rebuilt.

Information sheet no. 1

Troubleshooting chart- A guide in troubleshooting indicating specific
trouble, symptoms, probable cause and recommended actions to be taken.
Troubleshooting charts vary depending on the equipment and the particular
manufacturer. The guide does not cover all possible troubles and remedies that
may occur under conditions of operation.

TROUBLE SHOOTER’S GUIDE TO REFRIGERATION PROBLEMS

Symptoms Probable cause Recommended action

Trouble: Compressor Fails to Start

1. Electric-circuit test 1. Power failure 1. Check for blown line
shows the no. fuse of broken lead
current in line side
of motor starter.

2. Electric-circuit test 2. Disconnect switch 2. Determined why switch
shows no. current open was opened. If
on line side of everything ok, close
motor starter switch

3. Electric-circuit test 3. Fuse blown 3. Replace fuse. Check
shows current on load on motor.
line side of motor
side of fuse.

4. Electric-circuit tester 4. Low voltage 4. Check with voltmeter
glows but not at full then call power
brilliance. Company

5. Full voltage at motor 5. Burned-out motor 5. Repair or replace
terminals but motor
will not run.

6. Test for burned 6. Inoperative motor 6. Repair or replace

out holding coil starter

or broken contracts.

7. Motor starter holding 7. Open control circuit 7. Locate open control
coil is not energized a.) Dual pressure and determine Cause.
control See individual control

b.) Oil-failure control instructions.
c.) Motor starter

thermal overload
d.) Thermostat not Set

for cooling.
e.) open circuit from

“inter locking “relays

5.Excessively high 5. Faulty condensing 5.Check for water failure
discharge pressure or evaporative
6. Overcharge of frequent condenser trouble
6.High discharge or non condensable
pressure except too gas 6.Remove excess
frequent stopping and refrigerant or purge
starting on low 7. Lack of refrigerant non condensable gas
pressure control
switch 8. Water regulating value 7.Repair refrigerant leak
inoperative or and recharge
7.Normal operation restricted by dirt, or
except too frequent water temperature too 8.Clean or repair water
stopping and starting high value
on low pressure
control 9. Water piping restricted 9.Determined cause and
or supply water correct
8.High discharge pressure water
pressure pressure too low 10. Clean strainer

9. Discharge pressure 10. Restricted liquid line 11.Repair or replace
strainer faulty motor
10.Suction pressure too
low and frosting at 11. Faulty motor 12.Clean condenser tube
strainer
12. Fouled shell and tube 13.Determined cause
11.Motor start and condenser and correct
stops rapidly
13. Faulty operation of a.) Fill with water
12.Compressor cuts off evaporation condenser b.) Clean spray nozzles
on high pressure c.) Repair faulty pump
cutout

13.Compressor cuts off
on high pressure
cutout

a.) No water
b.) Spray nozzle

clogged d.) Clean coil
c.) Water pump not e.) Remove obstruction
f.) Repair
operating
d.) Coil surface dirty
e.) Air inlet or outlet

obstructed
f.) Fan not operating

Trouble: Compressor runs continuously

1.High temperature in 1. Excessive load 1.Check for excessive
conditioned space fresh air or infiltration.
2.Thermostat controlling Check for inadequate
2.Low temperature in at low a temperature insulation of space.
conditioned space in
3.”Welded” contracts on 2.Reset or repair the
3.Low temperature electrical controls in mostat
conditioned space monitor starter circuit
3.Repair or replace faulty
4.Bubbles in sight 4.Lack of refrigerant control
5.High discharge 5.Overcharge of
4.Repair leak and charge
pressure refrigerant 5.Purge or remove
6.Compressor noisy or 6.Leaky values in
excess
operating at compressor 6.Overhaul compressor
abnormally low
discharge pressure or 7.Solenoid stop value 7.Repair value or restore
abnormally high stuck open by manual to automatic operation
suction pressure lift stem
7.Air conditioned 8.Repair or replace.
spaced too cold 8.Broken or sheared Property realign
coupling
8.Motor runs but 9.Overhaul compressor
compressor does will 9.Frozen compressor due
not operate to lack or damage 10.check for loss of
mechanism refrigerant. Repair leak
9.Compressor will not and recharge
operate 10.Suction below cut in
setting of low pressure 11.Check condenser
10.Open contacts on cut out switch cooling water, fouled
low pressure switch. condenser,
Suction pressure 11.Discharge pressure
below cut-in setting above cut in setting of
high pressure cut out
11.Open contacts on
low pressure switch.
Above cut in setting

12.System will restart switch overcharged system
by resetting oil 12.Oil pressure failure 12.Check oil level. Oil
pressure failure
control switch control switch will cut pressure, wiring, ad
out control for faulty control

Trouble: Compressor “Short-Cycles

1. Normal operation 1. Intermittent contact in 1. Repair or replace
except electrical control faulty electrical control
Too frequent stopping circuit.
and starting 2. Reset differential in
2. Low-pressure Accordance with
2. Normal operation controller Different set proper job conditions
except too close
Too frequent stopping 3. Repair or replace
and starting 3. Leaky liquid solenoid
valve 4. Clean or defrost
3. Value may hiss when evaporator. Check
closed. Also 4. Dirty or iced filter and fan drive.
temperature change evaporator
in refrigerant line
through valve

4. Reduced air flow
A.) Dirty air filters
B.) Broken fan belt
C.) Fan belt
tension
improperly
adjusted

Trouble: Compressor losses Oil

1. Oil level too low 1. Insufficient oil charge 1. Oil sufficient amount
of proper compressor
2. Oil level gradually 2.Clogged strainer or oil
drops valves
2.Clean or repair and
3.Excessively cold 3.Loose expansion valve replace
suction noisy or remote bulb
compressor 3.Provide good contact
operation between remote bulb
and suction line
4.Excessively cold
suction noisy 4.Liquid flooding back to 4.Readjust superheat
compressor compressor setting or check
operation remote bulb contact

5.Too frequent starting 5.Short cycling 5.Defrost; check
and stopping of pressure cut out
compressor

6.Oil around
compressor based
and low and low

Self-check
To test your knowledge on troubleshooting PACU/CRE do the self-check

.
Direction: Given different troubles and symptoms of PACU/CRE Unit not
functioning efficiently, fill in the blanks the probable cause and recommended
action to be taken.

A. Trouble: Compressor fails to start

Symptoms Probable Cause Recommended Action

1. Electric circuit test
shows no current on
the line side of the
motor starter

2. Full voltage at motor
terminals but motor
not running

3. Excessive high
discharge pressure

4. Suction pressure too
low and frosting at
strainer

5. Compressor tripped-
off on high pressure
cut out.

B. Trouble; Compressor runs continuously

Symptoms Probable Cause Recommended Action
6. High temperature on

conditioned space

7. Bubbles on sight glass

8. Compressor not
functioning

C. Trouble: Compressor “Short Cycles”

Symptoms Probable Cause Recommended Action
9. Normal operation

except too frequent
stopping and starting

10. Valve when closed
produces a hissing
sound and
temperature change in
refrigerant line
through close solenoid
valve

Answer key

Probable cause Recommended trouble

1. Power failure 1. Check for blown fuse

2. Burned out motor 2. Repair or replace

3. Faulty condenser 3. Check condensing fan

4. Restricted liquid line strainer 4. Clean strainer

5. Fouled shell and tube condenser 5. Clean condenser tube

6. Excessive load 6. Check excessive fresh
or infiltration check for
inadequate insulation
of space

7. Lack of refrigerant 7. Repair leak and charge

8. Defective compressor 8. Overhaul compressor or change

9. Inter mitten in electrical control circuit 9. Repair or replace faulty
electrical control

10. Leaky liquid solenoid valve 10.Repair or replace

Troubleshoot a Hermetic Compressor Electric

Objectives: At the end of this practice, the learner/trainee will be able to:
 You will able to evaluate a motor in a hermetic compressor
to determine if it is electricity operational/functional

Materials, Tools and Equipment:

Information Sheet 1

Troubleshooting Unit When Compressor Fails to
Start

The most noticeable symptoms of a compressor not running are when the system
fails. Not functioning compressor can be detected and verified by using a voltmeter, ac clamp
ammeter and ohmmeter.

The voltmeter will be used to detect the presence of electromotive force (voltage) in
the terminal of the compressor. Lack of voltage means, the electrical path from the supply to
the compressor is open this is the reason why the compressor is not running. Low voltage
may also cause for the compressor not to run. Normal voltage means that the compressor
motor would function if it will draw current from the system.

The ammeter will be used to detect the current being drawn by compressor. The
reading will be compared to the compressor motor’s FLA and LRA. Lower current reading
means that the compressor is not drawing current from the source which is the reason for it
not to function. High current being drawn by the compressor means it is overload, which may
cause some protector to break the circuit and cut the supply going to the compressor.
Normal current means that the compressor motor is dissipating enough power to drive the
system.

Ohmmeter will be used to check and verify the condition of the compressor motor coil
out circuit. The continuity of the coil is checked because some technicians made mistakes in
jumping into conclusion that because the compressor does not draw current the compressor
motor coil is defective. There are cases wherein the reason why the compressor does not
draw current is because of loose connections in the compressor terminal. This mistake can
be eliminated by verifying the integrity of the compressor motor out circuit.

Three Major Probable Causes for a Compressor Motor Not to Function

There are three major probable causes for a compressor motor not to function; (1) the
electrical line that will supply the power for the motor is open; (2) the compressor motor is
defective or overloaded and; (3) the power supply is below than the required power of the
unit.

Among the three major probable causes, the first one is the trickiest to troubleshoot
because you need to trace the signal from the load side (terminals of the compressor motor)
to the line side (terminals of circuit protector). You need to find out where the signal stops
due to a defective component or protector design.

Information Sheet 1

Take the diagram above. The highlighted part is the compressor circuit. As you can
see, the signal path from the compressor terminal going to the source terminal passes
through different devices. If your going to trace the signal path you can see that from
terminal C of the compressor, the signal passes through the overload protection, going to
compressor switch (terminal 1 and 1A), then dual pressure control (terminal 3 to 1),
thermostat (terminal L and C), then main power switch (terminal 2B- 1B), then going through
the MCB and finally connected to L1. On the other hand the electrical path for S and R
terminal of the compressor passes through the current relay (Terminal S and M going to
terminal 1), then main power switch (terminal 2 A and 1) finally connected to L2.

To trace the signal from this circuit, you need test the presence of voltage in the
terminal of compressor, if there is you can assume the compressor it self is defective (see
operation sheet in testing compressor in the learning element compressor motor for more
details), if there is low voltage or non at all, you need to trace back the signal path from the
compressor to the supply line terminal (see operation sheet for signal tracing on this learning
element for more details).

The second major probable cause of trouble is simpler to troubleshoot. A defective
compressor motor can be caused by an open motor coil or shorted motor coil. Overloaded
compressor may have similar symptoms with shorted motor coil when tested in operation.
The open coil has the symptom of not drawing current from the source when checked with an

Information Sheet 1

ac clamp ammeter. To finally verify that the cause of trouble is really an open coil, continuity
of the coil must be checked using an ohm meter (see operation sheet in testing compressor
in the learning element compressor motor for more details).

The shorted coil or overloaded compressor however is a little bit trickier. The symptom
of these troubles is drawing excessive current from the supply source (more than 600% of
FLA rating) and probably tripping-off the protective device of the system when the unit is
tested for operation (power-on testing). To identify whether the compressor motor coil is
shorted, check the resistance of the coil. Although the normal resistance of the coil is very
low, shorted coil is still noticeable. Overloaded compressor however will have a non-shorted
coil but draws excessive current when energized. It may happen due to overcharging of
refrigerant, liquid slugging (liquid refrigerant returns to compressor during off cycle), air in the
system, changes in pressure in the low side and high side or partial stuck-up of crankshaft
due to lack of lubricant. This trouble basically is not compressor trouble, but the load and
effect falls in the compressor. Necessary corrective actions should be done (refer to the
learning element repair and retrofit for more details).

The third major probable cause is low voltage supply. This can be checked by using a
volt meter. The voltage supplied to the unit should not be less than or greater than 10% of
power rating of the unit (see nameplate of the unit). This trouble may be caused by a blown
fuse in supply line or trouble in the local power distribution.

Low voltage supply may cause severe damage to compressor due excessive current
drawn by the motor winding to compensate the power required by the unit therefore
protection device is essential to prevent the motor from overheating.

Information Sheet 1

Troubleshooting Unit When Compressor Fails to
Start (Single phase system)

Flow Chart Comment
Start
Note that the voltmeter is connected to line 1
Check the power and line 2 of the power supply while the main
supply power switch is in open position. This is to
ensure that the power supplied to the circuit is
the same with the unit’s requirement.

Yes Is the supply The power supplied to the unit should not be
1 appropriate less than 10% of the required supply of the unit
for the unit? (refer to unit’s nameplate)

No Since the supplied voltage is lower than the
required voltage of the unit the probable cause
Check fuse or is that the fuse or circuit breaker opened the
circuit breaker supply line (see operation sheet in checking
and replacing defective fuse from this learning
2 element for more details). Another probable
cause is a fault in the power distribution
system (call power distributor company).

2 Information Sheet 1

Yes Does this Checking the power terminal of the unit is
3 solve the necessary to ensure that the unit is not
problem? shorted. A shorted circuit when energized will
inflict further damage to the system.
No

Check power
terminal of the unit

for short circuit

Make sure that the main power is switched off
before measuring the resistance of the circuit.
An ohmmeter, connected to an energized
circuit will blow.

Yes Is the power
5 terminal
shorted?

No
4

Power On the Information Sheet 1
system
Turning of the power for the system is needed
Did the to trace where the signal stops.
compressor
hum (vibrate)? When the compressor hums, it means that the
power reaches the compressor; only it cannot
Check the power on C start maybe due to stuck-up, defective current
and R terminal of the relay or defective start winding (see checking
current relay and checking hermetic
compressor compressor).

Checking the signal on the terminal of the
compressor is needed to verify if the signal
from the supply line reaches the terminal of the
compressor motor.

Did the power
reached the

3 compressor
motor terminal?

Test the circuit
following the
diagram on the

right side

Information Sheet 1

Information Sheet 1

Troubleshooting Chart

Trouble: The unit is dead

Observable Symptoms:
 No power

2 Stop

Start Did the Does it have
unit the same
Check circuit
breaker if it trips function? symptom as
off before?
1
Reset the circuit 2
Test the unit for breaker,
operation
Is the
Did the circuit Refer to the othe
shorted? trouble shooting
No circuit Yes

breaker Check the load side of

tripped? the circuit breaker for

shorted

Measure the Locate the short
voltages at the in the circuit
landside of the
circuit breaker

Is the Yes Check the load side voltage of
voltage the circuit breaker

nor`m` al? Is the Yes Trace circuit for open 2
supply connection or loose
No normal? contact

Call power No Replace circuit
Distribution breaker
Company

2

Information Sheet 1

Trouble: Compressor does not start
Observed Symptoms: Compressor hums

Start 3 Yes

Check the Clamp Does it
power supply ammeter
installed in Did the have the
3 the mainline unit work No same
properly?
Stop Yes
Test unit for
operation symptom

1 as before?

Is the Call No
supply No operator
appropri Refer to the
ate for Distributor other
the unit? Company troubleshooting
for guide
assistance

Yes

Check current
relay/potential
relay

Is the 2
relay
defective No Is there a Yes Check
capacity capacitor
?`` Check wiring for 1
No Is the
Yes capacitor loose connection
2 defective?
Change Relay for open circuit in
Replace
Capacitor No the start of line Repair/

1 replace

compress

1 or motor

Is the loose No Check
connection motor
compress
on open or for
circuit? open
starting
Yes coil or
mechanic
Restore loose
connection open circuit al stuck up

1

Information Sheet 1

Troubleshooting Chart

Trouble: The unit is dead

Observable Symptoms:
 No power

2 Stop

Start Did the Does it have
unit the same
Check circuit
breaker if it trips function? symptom as
off before?
1
2
Test the unit for
operation

Did the Yes
circuit
breaker Reset the circuit
tripped? breaker,

No Check the load side of Is the Refer to the other
the circuit breaker for circuit trouble shooting guide
shorted shorted?

Measure the
voltages at the
landside of the
circuit breaker

Is the Yes Locate the short
voltage in the circuit

nor`m` al? Check the load side voltage of
the circuit breaker

No

Call power Is the Yes Trace circuit for open 2
Distribution supply connection or loose
Company normal? contact

No Replace circuit
2 breaker

Information Sheet 1

Trouble: Compressor does not start
Observable Symptoms: Compressor hums

Start 3 Yes

Check the Clamp Does it
power supply ammeter
installed in Did the have the
3 the mainline unit work No same
properly?
Stop Yes
Test unit for
operation symptom

1 as before?

Is the Call No
supply No operator
appropri Refer to the
ate for Distributor other
the unit? Company troubleshooting
for guide
assistance

Yes

Check current
relay/potential
relay

Is the 2
relay
defective No Is there a Yes Check
capacity capacitor
?`` Check wiring for 1
No Is the
Yes capacitor loose connection
2 defective?
Change Relay for open circuit in
Replace
Capacitor No the start of line Repair/

1 replace

compress

1 or motor

Is the loose No Check
connection motor
compress
on open or for
circuit? open
starting
Yes coil or
mechanic
Restore loose
connection open circuit al stuck up

1

Information Sheet 1

Troubleshooting Chart

Trouble: The unit does not start

Observable Symptoms:
 The circuit breaker keeps tripping off

Start

You can check the load
side for short circuit by
using an ohmmeter.

Check the load side of 3
the circuit breaker for

short circuit

Locate the short Reset the circuit
in the circuit breaker,

A good technique in 1 Test the unit for
locating short circuit is operation
by isolation. You
Is the Yes isolate the components
circuit which dissipate big
shorted? amount power then
measure their
No resistance. Some a
short circuit can be
caused by faulty wiring.

No Did the Yes
unit

Defective circuit breaker function?
may trip repeatedly even
Replace circuit though there is no short in Does it have 2 Stop
breaker the circuit the same

1 No symptom as
before?
Refer to other
troubleshooting guide Yes

3
2

Information Sheet 1

Trouble: The unit does not start

Observable Symptoms:
 Supply in the load side of the circuit breaker is normal
 Evaporator fan circuit, ok
 Condenser fan circuit, ok

Start Tracing back circuit can be done 2
visually or by measuring the
Check power in the continuity of the line
terminal of the
Does the supply No Trace-back circuit for
compressor, to verify if reach the loose wiring.
the signal reaches
compressor terminal of the
compressor?

Replace compressor Yes Restore Is there a
motor connection loose wiring?
If signal is present in the
terminal of the compressor, 1 Check controls and
therefore it is safe to assume protections for defects
that the compressor is defective
or troubles
Test the unit for Control and protection contacts
operation 1 are connected in series with the Repair/replace control
or protection
Did the Yes power line going to the
unit compressor. Defects from these 1
devices can cause the
function? compressor not to run

No Stop

Does it have 2
the same

symptom as
before?

No

Refer to other
troubleshooting guide

Information Sheet 1

Trouble: Compressor does not start (single phase motor)

Observable Symptoms: Open or loose connection in
 Compressor hums
 Supply is normal the start line may cause the
 High current
2 compressor not to start
Start because it will cut the current

going to the start winding.

Check current 3 Check loose or open
relay/potential connection at the start
Defective relay may cause line of the compressor Overload or stuck-up
relay compressor may cause the
compressor to hum Is there a compressor to hum and
Is the loose or open draws a large amount of
relay because it will cut the connection? No current.
defective?
No current flowing to start
winding.

Yes Is there a No Yes Check motor
Change Relay capacitor? compressor for
Restore loose open starting coil
connection open circuit or mechanical

stuck up

Yes 1
1 Repair/ replace

compressor motor

Check 1
capacitor
Defective capacitor may cause Refer to other
Is the compressor to hum because it
capacitor 2 will not be able to change the troubleshooting guide
defective? phase angle of the current No
flowing in the start winding which
Replace may prevent the rotor from Does it have
Capacitor revolving the same

1 symptom as
before?
Test unit for No
operation
Did the unit
work Yes Yes 3

properly?

Stop

Information Sheet 1

Trouble: Compressor runs continuously (air conditioner)
Observable Symptoms:

 No cooling effect on the evaporator
 High pressure on the high side of the unit

Start

Check if the condensing unit is Restricted condensing unit may cause
full of air restriction refrigeration and air conditioning not to
have cooling effect because there is no
Is it full of air complete condensation of refrigerant.
restriction?
Clean condensing unit 1
or remove any

restriction to the air
flow

Check if the condenser fan Maintain/ repair/ 2
replace condenser fan
1 motor requires maintenance/
motor
repair/ replacement
Defective condenser motor
Does the motor will have the same effect
require with restricted air flow in the
condensing unit
maintenance /
repair/

replacement?

Recover/ recycle
Refrigerant

Test run the unit 2 If the air flow is not restricted
and the fan motor is
functioning properly, the Change Filter
most probable cause of the
system not cooling is a
contaminated refrigerant.

Did the unit Evacuate the system
function
properly?

Re-charge the system

2

Stop

Information Sheet 1

Trouble: Compressor operate in short cycle
Observable Symptoms:

 Low cooling effect
 Frosting evaporator

Start

Check if there are restrictions Restricted evaporating unit may cause
in the air flow in the evaporator refrigeration and air conditioning to have
low cooling effect because there is no
unit complete evaporation of refrigerant.

Is there any Clean evaporator unit 1
restriction? or remove any

restriction to the air
flow

1 Check evaporator fan Defective evaporator fan will have the
motor same effect with restricted air flow in the
condensing unit
Maintain/ Repair/
Replace evaporator 2

motor

Does evaporator If the air flow is not restricted Recover/ recycle
fan motor require and the fan motor is Refrigerant
functioning properly, the
maintenance/ most probable cause of the Change Filter
repair/ system not cooling is a
contaminated refrigerant. Evacuate the system
replacement?

2 Test run the unit

Did the unit
function
properly?

Re-charge the system

2

Stop

Information Sheet 1

Trouble: Compressor runs continuously
Observable Symptoms:

 Low cooling effect
 Low pressure on the low side of the unit

Start

Check if there are restrictions Restricted evaporating unit may cause
in the air flow in the evaporator refrigeration and air conditioning to have
low cooling effect because there is no
unit complete evaporation of refrigerant.

Is there any Clean evaporator unit 1
restriction? or remove any

restriction to the air
flow

1 Check evaporator fan Defective evaporator fan will have the
motor same effect with restricted air flow in the
condensing unit
Maintain/ Repair/
Replace evaporator 2

motor

Does evaporator
fan motor require

maintenance/
repair/

replacement?

Leak in the system may also
cause the pressure to drop.

3 Leak test the unit Repair Leak 2

Is there a 3
leak?
Did the unit
2 function
properly?
Replace metering Test run the unit
device

Defective metering device may prevent Stop
refrigerant to build required pressure.

Information Sheet 1

Trouble: Compressor runs continuously
Observable Symptoms:

 Low cooling effect in the room temperature
 The running current of the current is normal

Start

Adjust the thermostat control Thermostat is a device used in controlling
of the unit to the coolest level the adjustment of temperature setting of
the unit. This adjustment is done to set
the unit to coolest setting.

Test-run the unit while

1 observing any charge in the
room temperature

Is the change Room insulation helps in Redesign air
in the room maintaining the cold air in the conditioning
temperature room. system for the
sufficient?
Check room room
Stop installation

Is the room
properly
insulated?

Add room 1
insulation

1

Information Sheet 1

Trouble: Compressor runs continuously
Observable Symptoms:

 Normal cooling effect
 Normal current

Start

Adjust the thermostat control
of the unit to the warmest
cool setting

Test-run the unit while

1 observing any charge in the
room temperature

Did the The thermostat should be
compressor placed where it can sense
the return air
turn off?
Check
positioning of

thermostat

Stop Is the sensing Replace
element in thermostat
proper
position? 1

Check positioning
of sensing
element

1

Job Sheet

Troubleshoot system with Compressor Operating
in Short Cycle

Objectives: At the end of this activity, the learner/trainee should be able to:
o Locate cause of trouble which causes compressor to operate in

short cycle.
o Restore PACU/CRE to normal operation
o Apply safety and proper work habit

Materials, Tools and Equipment:

Materials: - 1 set
o Cleaning materials for refrigeration and air-
- 1 cylinder
conditioning units
o Refrigerant R22/ R12 (depends on the unit - 1 set

to be used) - 1 set
o Learning element about Evaporator and - 1 set
- 1 set
Condenser Units
o Learning element about Fan Motors - 1 set
o Learning element about recover/recycle
o Learning element about tools and - 1 set

equipment used in refrigeration and air - 1 set
-
conditioning services 1 unit
o Learning element about charging - 1 unit
- 1 unit
PACU/CRE -
o Learning element about refrigeration 1 unit
- 1 unit
accessories - 1 unit
- 1 unit
Tools - 1 set
o Refrigeration ratchet -
o Wrench

Instrument
o Multi-tester
o Clamp ammeter
o Leak detector

Equipment
o Pressurize pump
o Recovery machine
o Vacuum pump
o Oxyacetylene Outfit
o PPE

- Item is optional-

Job Sheet

Introduction:
.

Procedure:
Make sure that before you perform this activity, you are wearing appropriate personal

protective equipment.

1. Ask your instructor on the unit to be used for this activity.

2. Analyze the attached chart to this activity. Follow the instruction in each process box
until such time that you repaired the air-conditioning unit assigned to you. You may
use several learning elements and learning module identified in this activity as your
reference in performing the required activity.

3. Let your instructor check your work.

4. Perform proper house keeping

Job Sheet

Trouble: Compressor operate in short cycle
Observable Symptoms:

 Low cooling effect
 Frosting evaporator

Start

Check if there are restrictions Restricted evaporating unit may cause
in the air flow in the evaporator refrigeration and air conditioning to have
low cooling effect because there is no
unit complete evaporation of refrigerant
(Refer to learning element in evaporator
Is there any and condenser unit).
restriction?
Clean evaporator unit 1
or remove any

restriction to the air
flow

1 Check evaporator fan Defective evaporator fan will have the
motor same effect with restricted air flow in the
condensing unit (Refer to learning
Maintain/ Repair/ element about fan motors)
Replace evaporator
2
motor

Does evaporator If the air flow is not restricted Recover/ recycle
fan motor require and the fan motor is Refrigerant
functioning properly, the
maintenance/ most probable cause of the Change Filter
repair/ system not cooling is a
contaminated refrigerant Evacuate the system
replacement? (Refer to learning module
about recover recycle, Re-charge the system
2 Test run the unit learning element in
refrigeration accessories,
Did the unit tools equipment used in
function refrigeration and air
properly? conditioning services and
charging PACU/CRE) .

2

Stop

Job Sheet

Evaluation:
While performing the activity it is important for you to assess your performance

following the criteria below: