1. Trouble Shooting and Performance Testing
CHAPTER
Trouble Shooting and Performance Testing 10
Instructor Name: (Your Name)

2. 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.

3. 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.

4. Learning Objectives (continued)
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.

5. Learning Objectives (continued)
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.

6. Learning Objectives (continued)
Explain the procedures for flushing an A/C sys.
Explain how to pop dry a system after a full flush has been performed.

7. 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.

8. 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

9. 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.

10. Servicing (continued)
Prior to any service work is performed, talk to drive to obtain any problematic history of the unit. Questions should include;
Did the A/C fail all at once or gradually loose its effectiveness?
Does the A/C work occasionally or not at all?
Has the A/C been worked on or serviced recently?

11. 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.

12. 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.

13. 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.

14. Troubleshooting Flow Chart

15. Manifold Gauge Set Connection

16. Pressure Temperature Chart

17. Gauge Reading, Some Air and Moisture in System

18. Gauge Reading, Some Air and Moisture in System
Symptoms
Not cooling effectively
Moisture indicator show moisture level high in system
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
Leak test the system
Remove refrigerant, repair any leaks found

19. Gauge Reading, Some Air and Moisture in System (continued)
Cure (continued)
Flush and purge system if required
Top up oil if required
Replace the receiver dryer
Evacuate the system
Charger with recommended weigh of refrigerant

20. Gauge Reading, Excessive Air and Moisture in System

21. Gauge Reading, Excessive Air and Moisture in System
Symptoms
Not cooling effectively
Moisture indicator show moisture level high in system
Suction pressure is high in the beginning but as system operates may drop to low or even vacuum
Discharge pressure is high
Cause
Receiver dryer saturated allowing moisture to freeze at the TXV
High pressure caused by excess air in system

22. Gauge Reading, Excessive Air and Moisture in System (continued)
Cure
Leak test the system
Reclaim refrigerant, repair any leaks
Flush and purge as required
Top up refrigerant oil
Replace receiver dryer
Evacuate system
Charge with recommended weight of refrigerant

23. Gauge Reading, Obstructed Condenser or Over Charged System

24. Gauge Reading, Obstructed Condenser or Over Charged System
Symptom
Not cooling effectively
Suction line warm
Discharge line too hot
Truck engine may be overheating
High pressure relief open opening circuit to clutch
Cause
Fan belt slipping, clutch fan faulty
Refrigerant is excessively overcharged

25. Gauge Reading, Obstructed Condenser or Over Charged System (continued)
Cure
Clean condenser and radiator, do not use a pressure washer
Check condition and tension of fan belt. Check fan speed and replace clutch fan if necessary
Recover refrigerant. Top up oil if necessary. Charge with recommended weight of refrigerant.
Test system pressure. If still high test for restriction in high side.

26. Gauge Reading, Low Refrigerant Charge

27. Gauge Reading, Low Refrigerant Charge
Symptoms
Not cooling effectively
Slightly lower than normal suction and discharge pressure
Cause
A very small leak in the A/C system
Cure
Leak test the system
Repair any leaks found
Flush and purge system if required

28. Gauge Reading, Low Refrigerant Charge(continued)
Cure
Top of oil if required
Replace receiver dryer
Evacuate the system
Charge with recommended weight of refrigerant

29. Gauge Reading, Very Low Refrigerant Charge

30. Gauge Reading, Very Low Refrigerant Charge
Symptoms
Not cooling
Discharge air from evaporator may be warm
Compressor not running or cycling frequently
Low pressure switch consistently open
Cause
Leak in air conditioning system
Cure
Leak test the A/C system

31. Gauge Reading, Very Low Refrigerant Charge (continued)
Cure (continued)
Recover refrigerant and repair any leaks
Flush and purge system if needed
Remove refrigerant and flush of required
Top off oil if required
Replace receiver dryer
Evacuate system
Charge with recommended weight of refrigerant

32. Gauge Reading, Restriction in High Side of System

33. Gauge Reading, Restriction in High Side of System
Symptom
Not cooling effectively
Frosted discharger line beyond restriction
If restriction is between compressor and inlet of receiver, discharge pressure may be excessively high
High pressure switch is open
Cause
Restriction between compressor discharge and inlet of TXV

34. Gauge Reading, Restriction in High Side of System (continued)
Cure
Feel discharge line for cold spots to identify the point of restriction
Recover refrigerant and flush of required
Replace defective component if it can’t be flushed
Top up oil if required
Replace receiver dryer
Evacuate system
Charge with recommended weight of refrigerant

35. Gauge Reading, TXV Not Opening Enough

36. Gauge Reading, TXV Not Opening Enough
Symptoms
Not cooling effectively
Sweat or frost build up on expansion valve
Suction or discharge pressure return to normal if heat is applied to TXV
Cause
The TXV does not open enough
The TXV is stuck closed
Problem with capillary tube or sensing bulb
Blockage at the orifice tube in CCOT system

37. Gauge Reading, TXV Not Opening Enough (continued)
Cure
Repair TXV if possible, if not go to Step 2
Recover refrigerant and flush system if required
Replace TXV, do not damage or crimp capillary tube
Top up refrigerant oil
Replace receiver dryer or accumulator
Evacuate system
Charge with recommended weight of refrigerant

38. Gauge Reading, TXV Held Open

39. Gauge Reading, TXV Held Open
Symptom
Not cooling effectively, cools well in beginning but evaporator freezes over and blocks air flow
Sweat or frost build up on TXV
Suction valve sweats heavily
System pressure returns to normal if evaporator is allowed to defrost
Cause
The TXV stuck open flooding evaporator
Problem with sensing bulb or capillary tube

40. Gauge Reading, TXV Held Open (continued)
Cure
Repair TXV if possible, if not go to Step 2
Recover refrigerant and flush if necessary
Replace TXV, be careful to not damage or crimp capillary tube
Top up oil if necessary
Replace receiver dryer
Evacuate the system
Charge with recommended weight of refrigerant

41. Gauge Reading, Defective Thermostatic Switch

42. Gauge Reading, Defective Thermostatic Switch
Symptoms
Not cooling effectively. Compressor runs constantly and may become noisy
Evaporator freezes up, blocking air flow
Cause
Defective thermostatic switch not disengaging clutch at temp below 32 degree f
Bent, kinked, or broken capillary tube causing thermostatic switch to malfunction

43. Gauge Reading, Defective Thermostatic Switch (continued)
Cure
Inspect condition of capillary tube for thermostatic switch.
Perform electrical test on the switch
Rectify any problems found with capillary tube
If capillary tube can’t be corrected, replace thermostatic switch

44. Gauge Reading, Defective Compressor

45. Gauge Reading, Defective Compressor
Symptoms
Not cooling effectively
Noisy compressor operation with no compressor cycling
Cause
Compressor drive belt loose or worn
Compressor clutch not operating
Internal compressor failure
Defective trinary or low pressure switch
Cure
Inspect/replace compressor drive belt
Inspect/replace engine drive pulley

46. Gauge Reading, Defective Compressor (continued)
Cure (continued)
Inspect/replace compressor clutch
Test trinary switch electrically, replace if necessary
If compressor is replaced, flush system
Top off oil if necessary
Replace receiver dryer
Evacuate system
Charge with recommended weight of refrigerant

47. 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.

48. 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.

49. 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.

50. 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.

51. 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.