A/C Request Circuit Check

Electrical Diagram:

CIRCUIT DESCRIPTION

This diagnostic is only for the 060 A/C system (manual control). For further diagnosis of the CJ2 system, refer to HVAC.

The A/C clutch relay is PCM controlled in order to delay the A/C clutch engagement after the system turns on the A/C. This allows the PCM to adjust the engine RPM before the A/C clutch engages. The PCM engages the A/C clutch any time the system requests the A/C 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, the system sends a 12 volt signal to the PCM. When the PCM receives this signal the PCM grounds the A/C clutch relay control circuit in order to energize the A/C relay. The scan tool shows this as A/C request YES.

When the PCM has detected a request for the A/C, the PCM grounds the A/C clutch relay control circuit, the relay contacts close, and current flows through the relay to the A/C compressor clutch.

When the PCM has detected a request for the A/C, the PCM turns on the cooling fan(s) when the 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. Testing and Inspection

3. The request circuit is shorted to a voltage it 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 it the test lamp did not illuminate. Refer to Body and Accessories/Wiring Systems or HVAC for further diagnosis.