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Home >> Oldsmobile >> 1999 >> Intrigue V6-214 3.5L VIN H SFI >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Testing and Inspection >> Component Tests and General Diagnostics >> A/C Request Circuit Diagnosis >> Without CJ2

Without CJ2









Circuit Description
The C67 A/C system (manual A/C), requests A/C operation via a wired A/C Request circuit between the HVAC control head and the PCM.

The A/C clutch relay is PCM controlled. 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.
^ Certain DTCs are set.

When the heater and A/C control is placed in the A/C mode, a 12 volt signal is sent to the PCM from the HVAC control head. This is shown on the scan tool as A/C Request Yes. The PCM will then ground the A/C clutch relay control circuit to energize the A/C relay (if none of the above conditions exist).

When the relay is energized, the relay contacts close, and current flows 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 reaches a predetermined pressure.

Diagnostic Aids
Before using this table, be sure no PCM DTC(s) are stored. The PCM may not activate the A/C clutch if certain DTCs are stored.

Use the Connector Test Adapter kit J 35616-A for any test that requires probing the PCM harness connectors, electrical center fuse/relay cavities, component terminals or a component harness connector. Using this kit will prevent damage caused by improper probing of connector terminals. If the problem is intermittent, refer to Intermittent Conditions for diagnosis. Intermittent Conditions

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 HVAC Blower Controls System Check in Heating and Air Conditioning for further diagnosis.

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