Insufficient Or No A/C Cooling
- Verify Condition
Check A/C system operation. Ensure refrigerant pressure is greater than 55 psi (3.9 kg/cm2 ). If system cools properly, instruct vehicle owner on proper use of system. If system does not cool properly, go to next step. - Check A/C Compressor Clutch
If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, go to COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS. - Check Cooling Fan
If vehicle is equipped with electric cooling fan, go to next step. If vehicle is not equipped with electric cooling fan, go to step 5). - Check Operation Of Cooling Fan
If electric cooling fan runs when A/C compressor clutch is engaged, go to next step. If electric cooling fan does not run when compressor clutch is engaged, see the ENGINE COOLING FAN article in the ENGINE COOLING section. - Component Checks
Check for loose, missing or damaged compressor drive belt. Check for loose or disconnected A/C clutch, cyclic switch or clutch cycling pressure switch wires and connectors. Check for damaged A/C clutch assembly.Check for blown fuses and disconnected resistor assembly. Check for proper operation of blower motor, vacuum motors and doors. Check for loose vacuum lines or misadjusted control cables (if equipped).
Ensure A/C control panel electrical and vacuum connections are secure. If any item is not functioning properly, repair as required and go to next step. If all items are functioning properly, go to step 7).
- Check System
If system now operates properly, fault conditions are corrected. Go to step 1). If system still does not operate properly, go to next step. - Check Compressor Clutch
Connect manifold gauge set. Set blower to highest speed. Set temperature control to full cool position. Close all doors and windows. Install thermometer at center discharge register. Record outside ambient temperature.Run engine at 1500 RPM with compressor clutch engaged. Stabilize A/C system with above conditions for about 10-15 minutes. Compare manifold gauge readings to normal system pressures. If clutch cycles properly and system pressure is within limits, A/C system is operating properly.
If compressor cycles rapidly (5 seconds on, 5 seconds off) and suction pressure is within limits, go to next step. If compressor runs continuously, go to step 9). A continuously running A/C compressor is considered normal when ambient temperature is greater than 80°F (27°C) and high humidity conditions.
If compressor cycles on above 52 psi (3.7 kg/cm2 ) and off below 21 psi (1.5 kg/cm2 ), replace A/C cyclic switch or clutch cycling pressure switch. After replacing switch, verify A/C system operation. If system still is not operating properly, reinstall original switch and go to next step.
- Check System
Check system for refrigerant leaks. If leaks exist in A/C system, repair leaks as required. Evacuate, recharge and verify A/C system operation.If leak does not exist in A/C system, check for a restricted orifice tube or liquid line. Also check for moisture or low refrigerant charge. Repair A/C system as required and verify A/C system operation.
- Check Clutch Cycling Pressure Switch
Disconnect blower motor connector. Check low pressure gauge for pressure at which clutch cycles off. If clutch cycles off between 22-25 psi (1.5-1.8 kg/cm2 ) and ambient temperature is more than 80°F (27°C), A/C system is operating properly.If clutch cycles off between 22-25 psi (1.5-1.8 kg/cm2 ) and ambient temperature is less than 80°F (27°C), recycle refrigerant A/C system. Evacuate, recharge and verify A/C system pressures. If clutch cycles off below 22 psi (1.5 kg/cm2 ), replace A/C cyclic switch or clutch cycling pressure switch. After replacing switch, verify A/C system operation.