Trouble Shooting and Performance Testing

Copyright © 2014 Delmar, Cengage Learning

Trouble Shooting and Performance Testing

Instructor Name: (Your Name)

10CHAPTER


Learning Objectives Identify proper safety equipment worn when

servicing HVACR systems. Explain how to work safely on pressurized

HVACR systems. List rules that should be followed whenever a

system has been opened to atmosphere. Explain how to performance test an HVACR

system.


Learning Objectives (continued)

Identify a system that contains some air and moisture.

Identify a system that has excessive air and moisture.

Identify a system that has restricted air flow through the condenser or is overcharged.

Identify a system that has a low refrigerant charge.



Identify a system that has a very low refrigerant charge.

Identify a system that is overcharged with refrigerant.

Identify a system that has a restriction in the high pressure side of system.

Identify a system that has a TXV that will not open.



Identify a system that has a TXV held open. Identify a system that has a defective

thermostat switch. Identify a system that has a defective

compressor. Identify the difference between purging and

flushing an A/C system. List the procedures for purging an A/C system.



Explain the procedures for flushing an A/C sys.

Explain how to pop dry a system after a full flush has been performed.


CAUTION

Air conditioning systems are always under pressure. Before internal system repairs are made refrigerant must be recovered from system. Once repairs are complete the system must be evacuated and recharged before it can be returned to service.


Air Conditioning Safety

Safety glasses Non leather gloves Proper ventilation Refrigerant must be stored below 125 degrees

Fahrenheit Refrigerant oil must be stored in air tight

containers Do not mix refrigerant oils


Servicing When system is open cap disconnected lines. Replace and lubricate all o-rings on

disconnected lines. Replace receiver dryer or accumulator on

opened system. Keep manifold gauge set connected when

servicing. Replace all lost refrigerant oil.


Servicing (continued) Prior to any service work is performed, talk to

drive to obtain any problematic history of the unit. Questions should include;1. Did the A/C fail all at once or gradually loose its

effectiveness?2. Does the A/C work occasionally or not at all?3. Has the A/C been worked on or serviced

recently?


Performance Testing Run engine at 1500 rpm, close all windows Run A/C on max for minimum 10 minutes to

stabilize system. Insert thermometer in air vent, let system stabilize Check for proper vent and fan operation. Visually inspect compressor, compressor clutch, and

drive belt. Feel the suction and discharge lines at compressor.

Suction line should be cold and discharge line should be hot.


Performance Testing Cont.

Feel condenser inlet and outlet line there should be a large change in temperature.

Feel condenser to receiver dryer line, feel for warm or cold spots.

Feel inlet and outlet of receiver dryer, they should be the same temperature.

Feel outlet of receiver dryer to TXV line, it should be a consistent temperature.


Performance Testing Cont.

Feel the suction line from evaporator to compressor, it should be cold.

If engine is running hot or heater water valve is stuck open the system will not cool.

Check discharge air temperature. It will vary according to ambient temp and humidity.

Shut down unit. Feel condenser for cold spots indicating

restrictions.


Troubleshooting Flow Chart


Manifold Gauge Set Connection


Pressure Temperature Chart


Gauge Reading, Some Air and Moisture in System


Gauge Reading, Some Air and Moisture in System

• Symptoms1. Not cooling effectively2. Moisture indicator show moisture level high in system3. Low pressure cycling does not respond to the on/off cycle

of thermostatic switch• Cause Air or moisture in system. Probably caused by external leak in

low side of the system.• Cure

1. Leak test the system2. Remove refrigerant, repair any leaks found


Gauge Reading, Some Air and Moisture in System (continued)

• Cure (continued)3. Flush and purge system if required4. Top up oil if required5. Replace the receiver dryer6. Evacuate the system7. Charger with recommended weigh of refrigerant


Gauge Reading, Excessive Air and Moisture in System


Gauge Reading, Excessive Air and Moisture in System

• Symptoms1. Not cooling effectively2. Moisture indicator show moisture level high in

system3. Suction pressure is high in the beginning but as

system operates may drop to low or even vacuum4. Discharge pressure is high• Cause1. Receiver dryer saturated allowing moisture to freeze

at the TXV2. High pressure caused by excess air in system


Gauge Reading, Excessive Air and Moisture in System (continued)

• Cure1. Leak test the system2. Reclaim refrigerant, repair any leaks3. Flush and purge as required4. Top up refrigerant oil5. Replace receiver dryer6. Evacuate system7. Charge with recommended weight of refrigerant


Gauge Reading, Obstructed Condenser or Over Charged System


Gauge Reading, Obstructed Condenser or Over Charged System

• Symptom1. Not cooling effectively2. Suction line warm3. Discharge line too hot4. Truck engine may be overheating5. High pressure relief open opening circuit to clutch• Cause1. Fan belt slipping, clutch fan faulty2. Refrigerant is excessively overcharged


Gauge Reading, Obstructed Condenser or Over Charged System (continued)

• Cure1. Clean condenser and radiator, do not use a pressure

washer2. Check condition and tension of fan belt. Check fan

speed and replace clutch fan if necessary3. Recover refrigerant. Top up oil if necessary. Charge

with recommended weight of refrigerant.4. Test system pressure. If still high test for restriction

in high side.


Gauge Reading, Low Refrigerant Charge


Gauge Reading, Low Refrigerant Charge

• Symptoms1. Not cooling effectively2. Slightly lower than normal suction and discharge

pressure• Cause1. A very small leak in the A/C system• Cure1. Leak test the system2. Repair any leaks found3. Flush and purge system if required


Gauge Reading, Low Refrigerant Charge(continued)

• Cure4. Top of oil if required5. Replace receiver dryer6. Evacuate the system7. Charge with recommended weight of refrigerant


Gauge Reading, Very Low Refrigerant Charge


Gauge Reading, Very Low Refrigerant Charge

• Symptoms1. Not cooling2. Discharge air from evaporator may be warm3. Compressor not running or cycling frequently4. Low pressure switch consistently open• Cause1. Leak in air conditioning system• Cure1. Leak test the A/C system


Gauge Reading, Very Low Refrigerant Charge (continued)

• Cure (continued)2. Recover refrigerant and repair any leaks3. Flush and purge system if needed4. Remove refrigerant and flush of required5. Top off oil if required6. Replace receiver dryer7. Evacuate system8. Charge with recommended weight of refrigerant


Gauge Reading, Restriction in High Side of System


Gauge Reading, Restriction in High Side of System

• Symptom1. Not cooling effectively2. Frosted discharger line beyond restriction3. If restriction is between compressor and inlet of

receiver, discharge pressure may be excessively high4. High pressure switch is open• Cause1. Restriction between compressor discharge and inlet

of TXV


Gauge Reading, Restriction in High Side of System (continued)

• Cure1. Feel discharge line for cold spots to identify the

point of restriction2. Recover refrigerant and flush of required3. Replace defective component if it can’t be flushed4. Top up oil if required5. Replace receiver dryer6. Evacuate system7. Charge with recommended weight of refrigerant


Gauge Reading, TXV Not Opening Enough


Gauge Reading, TXV Not Opening Enough

• Symptoms1. Not cooling effectively2. Sweat or frost build up on expansion valve3. Suction or discharge pressure return to normal if

heat is applied to TXV• Cause1. The TXV does not open enough2. The TXV is stuck closed3. Problem with capillary tube or sensing bulb4. Blockage at the orifice tube in CCOT system


Gauge Reading, TXV Not Opening Enough (continued)

• Cure1. Repair TXV if possible, if not go to Step 22. Recover refrigerant and flush system if required3. Replace TXV, do not damage or crimp capillary tube4. Top up refrigerant oil5. Replace receiver dryer or accumulator6. Evacuate system7. Charge with recommended weight of refrigerant


Gauge Reading, TXV Held Open


Gauge Reading, TXV Held Open

• Symptom1. Not cooling effectively, cools well in beginning but

evaporator freezes over and blocks air flow2. Sweat or frost build up on TXV3. Suction valve sweats heavily4. System pressure returns to normal if evaporator is

allowed to defrost• Cause1. The TXV stuck open flooding evaporator2. Problem with sensing bulb or capillary tube


Gauge Reading, TXV Held Open (continued)

• Cure1. Repair TXV if possible, if not go to Step 22. Recover refrigerant and flush if necessary3. Replace TXV, be careful to not damage or crimp

capillary tube4. Top up oil if necessary5. Replace receiver dryer6. Evacuate the system7. Charge with recommended weight of refrigerant


Gauge Reading, Defective Thermostatic Switch


Gauge Reading, Defective Thermostatic Switch

• Symptoms1. Not cooling effectively. Compressor runs constantly

and may become noisy2. Evaporator freezes up, blocking air flow• Cause1. Defective thermostatic switch not disengaging

clutch at temp below 32 degree f2. Bent, kinked, or broken capillary tube causing

thermostatic switch to malfunction


Gauge Reading, Defective Thermostatic Switch (continued)

• Cure1. Inspect condition of capillary tube for thermostatic

switch.2. Perform electrical test on the switch3. Rectify any problems found with capillary tube4. If capillary tube can’t be corrected, replace

thermostatic switch


Gauge Reading, Defective Compressor


Gauge Reading, Defective Compressor

• Symptoms1. Not cooling effectively2. Noisy compressor operation with no compressor cycling• Cause1. Compressor drive belt loose or worn2. Compressor clutch not operating3. Internal compressor failure4. Defective trinary or low pressure switch• Cure1. Inspect/replace compressor drive belt2. Inspect/replace engine drive pulley


Gauge Reading, Defective Compressor (continued)

• Cure (continued)3. Inspect/replace compressor clutch4. Test trinary switch electrically, replace if necessary5. If compressor is replaced, flush system6. Top off oil if necessary7. Replace receiver dryer8. Evacuate system9. Charge with recommended weight of refrigerant


Flushing and Purging

Purging blows out wet air, refrigerant, and loose dirt from system

Flushing is used to clean extremely contaminated systems.

Purging, use dry nitrogen. HCFC 141b. Is commonly approved by system

manufacturers Some manufactures do not endorse flushing and

are not covered under their warranty.


Summary A/C systems are constantly under pressure. Always wear appropriate PPE when working

on a charged A/C system R-134a can be combustible under the right

conditions. A/C system should never be pressure or leak

tested with compressed air, a fire or explosion could result.


Summary cont. PAG oil containers should always be kept

tightly closed. When a system is open, always cap

disconnected lines. Whenever A/C lines are disconnected always

replace and lubricate o-rings. Receiver driers must be replaced when a system

is opened. Manifold gauge fittings should be connected to

manifold when not in use.


Summary cont. Add refrigerant oil to replace any that may have

been lost. Always question operator about problems and

history of problems. Performance tests identify problems that may

exist. To check levels of R-134a, a performance test

with gauge set must conducted. If refrigerant is low, repair leaks, recover all coolant and refill. DO NOT TOP OFF SYSTEM.


Summary cont.

Use dry nitrogen to purge wet air and loose dirt from and A/C system.

Use liquid flushing agents to clean contaminants from A/C components.

Popping components dry is a process of drying A/C components with quick shots of dry nitrogen.

Trouble Shooting and Performance Testing

Documents

ac system

opened system

system stabilizecheck

internal system repairs

ac work

refrigerant oilscopyright

windowsrun ac

low refrigerant charge