Pinpoint Test L: The Air Conditioning (A/C) Is Always On - A/C Compressor Does Not Cycle

Climate Control System

Pinpoint Tests

Pinpoint Test L: The Air Conditioning (A/C) is Always On - A/C Compressor Does Not Cycle

Refer to Wiring Diagram Set 54, Manual Climate Control System for schematic and connector information. Diagrams By Number

Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information. Diagrams By Number

Normal Operation

Under normal operation, when A/C is requested, a message is sent from the HVAC module over the Medium Speed Controller Area Network (MS-CAN) bus to the PCM. Ignition voltage is provided to the A/C clutch relay switch through circuit SBB24 (VT/RD). When the PCM energizes the relay, ignition voltage is supplied to the A/C clutch through circuit CH421 (GY). Ground is supplied for the A/C clutch through circuit GD120 (BK/GN).

This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- PCM
- HVAC module - Dual Automatic Temperature Control (DATC)
- HVAC module - Electronic Manual Temperature Control (EMTC)
- A/C evaporator discharge temperature sensor
- A/C control relay
- A/C clutch air gap



PINPOINT TEST L: THE AIR CONDITIONING (A/C) IS ALWAYS ON - A/C COMPRESSOR DOES NOT CYCLE

NOTE: Before carrying out the following test, diagnose any PCM or Instrument Cluster (IC) DTCs.

NOTE: When disconnecting and reconnecting the pressure transducer electrical connector, make sure that the connector-locking device is in place and that the locking device and connector are correctly and fully seated.

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L1 CHECK THE A/C EVAPORATOR TEMPERATURE (EVAP_TEMP) HVAC PID


- Ignition ON.
- Allow the vehicle exterior and interior to stabilize to an ambient temperature above 16°C (60°F).
- Enter the following diagnostic mode on the scan tool: EVAP_TEMP HVAC PID.
- Does the EVAP_TEMP HVAC PID read similar to the ambient temperature?

Yes
GO to L2.

No
INSTALL a new A/C evaporator discharge temperature sensor. TEST the system for normal operation.

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L2 CHECK THE AIR CONDITIONING CLUTCH (WAC/ACCR) PCM PID WITH THE A/C OFF


- Enter the following diagnostic mode on the scan tool: WAC/ACCR PCM PID.
- Does the WAC/ACCR PCM PID read ON?

Yes
GO to L5.

No
GO to L3.

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L3 CHECK FOR VOLTAGE TO THE A/C COMPRESSOR CLUTCH FIELD COIL


- Ignition OFF.
- Disconnect: A/C Compressor Clutch Field Coil C100.
- Ignition ON.
- Select the OFF position on the HVAC module.
- With the engine running, measure the voltage between A/C compressor clutch field coil C100-1, circuit CH421 (GY), harness side and ground.




- Is the voltage greater than 10 volts?

Yes
GO to L4.

No
ADJUST the A/C compressor clutch gap. REFER to Air Conditioning (A/C) Clutch Air Gap Adjustment Adjustments. TEST the system for normal operation.

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L4 CHECK CIRCUIT CH421 (GY) FOR A SHORT TO VOLTAGE


- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- Ignition ON.
- Measure the voltage between A/C compressor clutch field coil C100-1, circuit CH421 (GY), harness side and ground.




- Is the voltage greater than 10 volts?

Yes
REPAIR circuit CH421 (GY) for a short to voltage. TEST the system for normal operation.

No
INSTALL a new A/C clutch relay. TEST the system for normal operation.

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L5 CHECK THE PCM CONNECTION


- Clear the DTCs.
- Disconnect all of the PCM connectors.
- Check for:
- corrosion.
- pushed-out connectors.
- incorrectly seated connector.
- Connect and correctly seat all of the PCM connectors.
- Operate the system.
- Does the concern return?

Yes
INSTALL a new PCM. TEST the system for normal operation.

No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.

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