Symptom Related Diagnostic Procedures

System Symptoms

There are four basic symptoms associated with air conditioning fault diagnosis. A slightly different approach to problem solving will be necessary since the deletion of the sight glass. It is very important to positively identify the area of concern before starting a rectification procedure. A little time spent with your customer on problem identification, and use of the following trouble shooting guides will be beneficial.

The following conditions are not in order of priority.

No Cooling
1. Is the electrical circuit to the compressor clutch functional?
2. Is the electrical circuit to the blower motor(s) functional?
3. Slack or broken compressor drive belt.
4. Compressor partially or completely seized.
5. Compressor shaft seal leak.
6. Compressor valve or piston damage (may be indicated by small variation between HIGH & LOW side pressures relative to engine speed).
7. Broken refrigerant pipe (causing total loss of refrigerant).
8. Leak in system (causing total loss of refrigerant).
9. Blocked filter in the receiver/dryer.

Insufficient Cooling
1. Blower motor(s) sluggish.
2. Restricted blower inlet or outlet passage.
3. Blocked or partially restricted condenser matrix or fins.
4. Blocked or partially restricted evaporator matrix or filter.
5. Blocked or partially restricted filter in the receiver/dryer.
6. Blocked or partially restricted expansion valve.
7. Partially collapsed flexible pipe.
8. Expansion valve temperature sensor faulty (this sensor is integral with the valve and is not serviceable).
9. Excessive moisture in the system.
10. Air in the system.
11. Low refrigerant charge.
12. Compressor clutch slipping.

Intermittent Cooling
1. Is the electrical circuit to the compressor clutch consistent?
2. Is the electrical circuit to the blower motor(s) consistent?
3. Compressor clutch slipping.
4. Faulty air distribution flap potentiometer or motor.
5. Motorized in-car aspirator or evaporator temperature sensor faulty, causing temperature variations.
6. Blocked or partially restricted evaporator or condenser.

Noisy System
1. Loose or damaged compressor drive belt.
2. Loose or damaged compressor mountings.
3. Compressor oil level low, look for evidence of leakage.
4. Compressor damage caused by low oil level or internal debris.
5. Blower(s) motor(s) noisy.
6. Excessive refrigerant charge, witnessed by vibration and "thumping" in the high pressure line (may be indicated by high HIGH & high LOW side pressures).
7. Low refrigerant charge causing "hissing" at the expansion valve (may be indicated by low HIGH side pressure).
8. Excessive moisture in the system causing expansion valve noise.

NOTE: Electrical faults may be more rapidly traced using JDS.