Preparation For Testing
- Attach Low and High Side gauges to system.
- Start engine and warm to operating temperature.
- Set system to Cool and blower to High.
- Open car doors and hood.
- Run at fast idle for 2-3 minutes before check.
Air Conditioning System Performance Check
| PERFORM TESTS: | SHOULD BE: | IF: |
|---|---|---|
| Temperature Check | Temperature Check is: | |
|
35-45° F | Too warm, check function of control levers, heater water valve, cooling system and gauge readings. |
| Visual Check | Visual Check Shows: | |
|
No excess noise; no leaks | Noisy, check belts, oil level, seals, gaskets, bearing, reed valves. |
|
Free of obstructions | Blocked, clean off debris. Plugged, flush with R-12 or replace. |
|
Dry; warm to touch | Frosty, check for restriction or moisture saturation. Replace desiccant. |
|
Clear or few bubbles | Bubbly, foamy or streaky, check reference manual and gauge readings. |
|
Dry; warm to touch; no leaks | Frosty or very hot, check for restriction condenser malfunction or R-12 overcharge. |
|
Dry | Frosty, check for moisture or restriction. Check sensing bulb. |
|
Dry; cold to touch | Freezing or warm, check for expansion valve, thermostatic switch or STV malfunction. |
|
Dry; cool to touch | Frosty or warm, check for valve malfunction. Check gauge readings. |
|
Dry; cool to touch; no leaks | Frosty or warm, check for restriction, low R-12 charge, or valve malfunction. |
| Gauge Readings | Gauge Readings are: | |
|
See Figure. | Above or below normal, refer to "Air Conditioning Diagnosis " chart. |
|
See Figure. | Above or below normal, refer to "Air Conditioning Diagnosis " chart. |
NOTE:
For diagnosis with gauges, refer to chart on following page.
Air Conditioning Diagnosis With Gauges For System With Insufficient Or No Cooling
| Low Side Gauge | High Side Gauge | Other Symptoms(1) | Diagnosis | ||
|---|---|---|---|---|---|
| NORMAL | NORMAL | No or few bubbles in sight glass. High side gauge may go high. Low side gauge does not fluctuate with compressor on/off cycle. | Some Air and Moisture in System | ||
| NORMAL | NORMAL | Cools okay in morning, but not during hot part of day. Tiny bubbles in sight glass. Discharge air warm when low side gauge drops into vacuum. | Excessive Moisture in System | ||
| NORMAL | NORMAL | Thermostatic switch system only: Compressor cycles on and off too rapidly. | Defective Thermostatic Switch | ||
| NORMAL to HIGH | NORMAL | Cycling clutch systems only: Compressor doesn't turn on soon enough. Discharge air becomes warm as low side pressure builds. | Misadjusted Thermostatic Switch or Defective Pressure Sensing Switch | ||
| LOW | LOW | Bubbles in sight glass. Outlet air slightly cool. | Low R-12 Charge | ||
| LOW | LOW | Sight glass clear. Outlet air very warm or same as outside air temp. | Excessively low R-12 Charge | ||
| LOW | LOW | Outlet air slightly cool. Sweating or frost at expansion valve. | Expansion Valve Stuck Closed, Screen Plugged or Sensing Bulb Malfunction | ||
| LOW | LOW | Outlet air slightly cool. High side line cool to touch. Sweating or frost on high side. | Restriction in High Side. | ||
| LOW | HIGH | Evaporator outlet pipe cold. Low side goes info vacuum when blower is disconnected. | STV Stuck Open | ||
| HIGH | LOW | Evaporator outlet pipe worm. Outlet air warm. | STV Stuck Closed | ||
| HIGH | LOW | Noise from compressor. | Compressor Malfunction (Internal Leak) | ||
| HIGH | HIGH | Outlet air warm. Liquid line very hot. Bubbles in sight glass. | Condenser Malfunction or R-12 Overcharge | ||
| HIGH | HIGH | Outlet air slightly cool. Bubbles in sight glass. | Large Amount of Air and Moisture in System | ||
| HIGH | HIGH | Outlet air warm. Evaporator and outlet pipe show sweating and frost. | Expansion Valve Stuck Open | ||
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