Air Conditioning System Performance Check
- Attach Gauge Set
- High Side
- Low Side
- Auxiliary Gauge (if used)
- Stabilize System
- Start Engine
- Set Controls to Max. Cool.
- Blower Speed to High.
- Open Car Doors.
- Engine to Fast idle.
- Temperature Check
- Switch to Low Blower.
- Close Doors.
- Check Outlet Air Temperature.
- Check Ambient Air Temperature.
- Visual Check
- Compressor
- Condenser
- Receiver-Drier
- Sight Glass
- High Side Lines
- Expansion Valve
- Evaporator
- POA/STV
- Low Side Lines
- Gauge Readings
- High Side Gauge
- Low Side Gauge
- Auxiliary Gauge (if used)
| SHOULD BE | IF... |
| Temperature Check is: | |
| 35-45°F See TEMPERATURE CHART . |
Too warm, check function of control levers, heater water valve, cooling system and gauge readings. |
| Visual Check Shows: | |
| No excess noise; no leaks | Noisy, check belts, oil level, seals, gaskets, bearing, reed valves. Check gauge readings. |
| Free of obstructions | Blocked, clean off debris. Plugged, flush with R-12 or replace. Check gauge readings. |
| Dry; warm to touch | Frosty, check for restriction or moisture saturation. Check gauge readings. 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. Check gauge readings. |
| Dry | Frosty, check for moisture or restriction. Check sensing bulb. Check gauge readings. |
| Dry; cold to touch | Freezing or warm, check for expansion valve, thermostatic switch or POA/STV or EPR valve malfunction. Check gauge readings. |
| 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. Check gauge readings. |
| Gauge Readings are: | |
| See PRESSURE CHART . See PRESSURE CHART . See PRESSURE CHART . |
Above or below; normal, refer to "AIR CONDITIONING DIAGNOSIS " chart. Above or below; normal, refer to "AIR CONDITIONING DIAGNOSIS " chart. Above or below; normal, refer to "AIR CONDITIONING DIAGNOSIS " chart. |
Air Conditioning Diagnosis for Systems with Insufficient or No Cooling
| Low Side Gauge | High Side Gauge | Auxiliary Gauge (if used)(1) | Other Symptoms(2) | Diagnosis | ||||
|---|---|---|---|---|---|---|---|---|
| NORMAL | 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 | NORMAL | Cools okay in morning, but not during hot part of day. Tiny bubbles in sight glass. Discharge air warm when low side gouge 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 | ..... | Thermostatic switch system only: Compressor doesn't turn on soon enough. Discharge air becomes warm as low side pressure builds. |
Misadjusted Thermostatic Switch | ||||
| LOW | LOW | LOW | Bubbles in sight glass. Outlet air slightly cool. |
Low R 12 Charge | ||||
| LOW | LOW | LOW | Sight glass clear. Outlet air very warm or same as outside air temp. |
Excessively Low R 12 Charge | ||||
| LOW | LOW | LOW | Outlet air slightly cool. Sweating or frost at expansion valve. |
Expansion Valve Struck Closed, Screen Plugged or Sensing Bulb Malfunction | ||||
| LOW | LOW | LOW | Outlet air slightly cool. High side line cool to touch. Sweating or frost on high side. |
Restriction in High Side. | ||||
| LOW | HIGH | HIGH | Evaporator outlet pipe cold. Low side goes into vacuum when blower is dosconnected. |
POA/STV or EPR Valve Stuck Open | ||||
| HIGH | LOW | LOW | Evaporator outlet pipe warm. Outlet air warm. |
POA/STV or EPR Valve Stuck Closed | ||||
| HIGH | LOW | LOW | Noise from compressor. | Compressor Malfunction (Internal Leak) | ||||
| HIGH | HIGH | HIGH | Outlet air warm. Liquid line very hot. Bubbles in sight glass. |
Condenser Malfunction or R-12 Overcharge | ||||
| HIGH | HIGH | HIGH | Outlet air slightly cool. Bubbles in sight glass. |
Large Amount of Air and Moisture in System | ||||
| HIGH | HIGH | HIGH | Outlet air warm. Evaporator and outlet pipe show sweating and frost. |
Expansion Valve Stuck Open | ||||
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