Pinpoint Test M: The Air Conditioning (A/C) Is Always On - A/C Compressor Does Not Cycle
Climate Control System
Pinpoint Tests
Pinpoint Test M: 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, for Dual Automatic Temperature Control (DATC) systems, when A/C is requested, the HVAC module - DATC sends an A/C request message over the Medium Speed Controller Area Network (MS-CAN) bus to the Instrument Cluster (IC), then from the IC through the High Speed Controller Area Network (HS-CAN) bus to the PCM.
Under normal operation, for manual climate control systems, when A/C is requested, a voltage is supplied to the PCM on the A/C request PCM input.
The PCM also receives a ground from the A/C cycling switch when pressures are sufficient to close the switch. Ground is provided to the A/C cycling switch.
Voltage is provided to the A/C clutch relay switch. When the PCM energizes the relay, voltage is supplied to the A/C clutch from the relay. Ground is supplied for the A/C clutch.
The A/C cycling switch is used for A/C compressor cycling. The A/C cycling switch is used by the PCM to turn off the A/C compressor when the refrigerant pressure is low enough to make the evaporator temperatures cold enough to freeze the condensation. The A/C pressure transducer is used to turn off the A/C compressor when the refrigerant pressure is to high. Excessively high refrigerant pressure can damage the A/C compressor.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- PCM
- A/C compressor clutch field coil
- A/C control relay
- A/C clutch air gap
PINPOINT TEST M: THE AIR CONDITIONING (A/C) IS ALWAYS ON - A/C COMPRESSOR DOES NOT CYCLE
NOTE: Before carrying out the following test, diagnose any HVAC, PCM or IC DTCs.
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M1 CHECK THE AIR CONDITIONING CLUTCH (WAC/ACCR) PCM PID WITH THE A/C ON
- Ignition ON.
- Place the function selector switch to the OFF position.
- Enter the following diagnostic mode on the scan tool: WAC/ACCR PCM PID.
- Does the WAC/ACCR PCM PID read OFF?
Yes
GO to M2.
No
GO to M6.
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M2 CHECK THE AIR CONDITIONING COMPRESSOR DIAGNOSTIC SWITCH (ACDS1) PCM PID
- Ignition OFF.
- Disconnect: A/C Cycling Switch C130.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: ACDS1 PCM PID.
- Observe the ACDS1 PCM PID.
- Does the ACDS1 PCM PID read DISABLE?
Yes
GO to M3.
No
REPAIR circuit CH423 (YE) for a short to ground. TEST the system for normal operation.
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M3 CHECK THE A/C CYCLING SWITCH
- Ignition OFF.
- Remove the A/C cycling switch from the vehicle.
- Measure the resistance between the A/C cycling switch terminals.
- Is the resistance greater than 10,000 ohms?
Yes
GO to M4.
No
INSTALL a new A/C cycling switch. TEST the system for normal operation.
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M4 CHECK FOR VOLTAGE TO THE A/C COMPRESSOR CLUTCH FIELD COIL
- Ignition OFF.
- Disconnect: A/C Compressor Clutch Field Coil C1110.
- Ignition ON.
- With the engine running, measure the voltage between ground and A/C compressor clutch field coil C1110-1, circuit CH401 (VT/WH) (4.0L) or CH401 (GY/WH) (4.6L), harness side.
- Is any voltage present?
Yes
GO to M5.
No
ADJUST the A/C compressor clutch air gap. REFER to Air Conditioning (A/C) Clutch Air Gap Adjustment Adjustments. TEST the system for normal operation.
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M5 CHECK THE A/C CONTROL RELAY
- Ignition OFF.
- Disconnect: A/C Control Relay.
- Ignition ON.
- With the engine running, measure the voltage between ground and A/C compressor clutch field coil C1110-1, circuit CH401 (VT/WH) (4.0L) or CH401 (GY/WH) (4.6L), harness side.
- Is any voltage present?
Yes
REPAIR circuit CH401 (VT/WH) for a short to voltage. TEST the system for normal operation.
No
INSTALL a new A/C control relay. TEST the A/C clutch diode. INSTALL a new diode, if necessary. TEST the system for normal operation.
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M6 CHECK THE PCM CONNECTION
- Clear the DTCs.
- Disconnect all the PCM connectors.
- Check for:
- corrosion.
- pushed-out pins.
- incorrectly seated connector.
- Connect and correctly seat all 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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