A/C Request Circuit Diagnosis

Circuit Description:
This diagnostic is only for the C60 A/C system (manual control). For further diagnosis of the CJ2 system, refer to HVAC.

The A/C clutch relay is PCM controlled to delay A/C clutch engagement after the A/C is turned ON. This allows the PCM to adjust engine RPM before the A/C clutch engages. The PCM will engage the A/C clutch any time A/C has been requested unless any of the following conditions exist:
^ High coolant temperature.
^ Low A/C system pressure.
^ High A/C system pressure.
^ Wide open throttle.
^ High engine RPM.

When the heater and A/C control is placed in the A/C mode, a 12 volt signal is sent to the PCM. When the PCM receives this signal the PCM will ground the A/C clutch relay control circuit to energize the A/C relay. This is shown on the scan tool as A/C request YES.

When a request for A/C has been detected by the PCM, the PCM will ground the A/C clutch relay control circuit, the relay contacts will close and current will flow through the relay to the A/C compressor clutch.

When A/C request has been detected by the PCM, the cooling fan(s) will be turned ON when A/C pressure is above a predetermined pressure.

Diagnostic Aids
Before using this table, be sure no PCM DTC(s) are stored. The PCM will not activate the A/C clutch with a stored DTC.

Test Description
The numbers below refer to numbers on the diagnostic table.
2. A/C DTCs will disable the A/C system. Repair A/C DTCs before proceeding.
3. The request circuit is shorted to a voltage if the scan tool displays A/C request as YES.
5. A problem exists with the request circuit between the PCM and the HVAC Programmer or the HVAC Programmer is malfunctioning if the test lamp did not illuminate. Refer to Body and Accessories/wiring Systems or HVAC for further diagnosis.