A/C Request Circuit Check

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION:
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
Ensure no PCM DTC(s) are stored before using this table. 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 Electrical Diagnosis/Repair Procedures or HVAC for further diagnosis.