Pinpoint Test J: The Air Conditioning (A/C) is Always On - A/C Compressor Does Not Cycle
Climate Control System
Pinpoint Tests
Pinpoint Test J: 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, the HVAC module 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.
For gasoline engines, voltage is provided to the high-pressure cutoff switch. If the high-pressure cutoff switch is closed (pressure not excessive), voltage is sent to the A/C cycling switch. If the A/C cycling switch is closed (sufficient pressure) voltage is sent from the A/C cycling switch to the PCM.
For diesel engines, voltage is provided to the A/C cycling switch. If the A/C cycling switch is closed (sufficient pressure) voltage is sent from the A/C cycling switch to the dual-function pressure switch. If the dual-function pressure switch is closed (pressure not excessive), voltage is sent to the PCM.
For all engines, when the PCM receives voltage from the pressure switches, the PCM provides a ground for the A/C clutch relay. Voltage is provided to the A/C clutch relay switch. When the PCM energizes the relay by grounding it, 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. This prevents ice blockage of airflow over the evaporator core.
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 cycling switch
- A/C control relay
- A/C clutch air gap
PINPOINT TEST J: 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.
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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J1 CHECK THE AIR CONDITIONING CLUTCH (WAC/ACCR) PCM PID WITH THE A/C OFF
- Start the engine.
- Enter the following diagnostic mode on the scan tool: WAC/ACCR PCM PID.
- With the engine running and A/C button OFF:
- (EMTC systems) Select PANEL mode.
- (DATC systems) Press the PANEL override button.
- Does the WAC/ACCR PCM PID read OFF?
Yes
GO to J4.
No
GO to J2.
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J2 CHECK THE AIR CONDITIONING CLUTCH ALLOWED (ACCLT_ALW) PCM PID
- Ignition OFF.
- Disconnect: A/C Cycling Switch C1081.
- Start the engine.
- Enter the following diagnostic mode on the scan tool: ACCLT_ALW PCM PID.
- With the engine running and A/C button OFF:
- (EMTC systems) Select PANEL mode.
- (DATC systems) Press the PANEL override button.
- Does the ACCLT_ALW PCM PID read YES?
Yes
For gasoline engines, REPAIR circuit CH421 (GY) for a short to voltage. TEST the system for normal operation.
For diesel engines, GO to J3.
No
GO to J6.
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J3 CHECK CIRCUIT CH421 (GY) FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: Dual-Function Pressure Switch C1062.
- Disconnect: PCM C1232e.
- Ignition ON.
- Measure the voltage between ground and PCM C1232e-36, circuit CH421 (GY), harness side.
- Is any voltage present?
Yes
REPAIR circuit CH401 (VT/WH) for a short to voltage. TEST the system for normal operation.
No
REPAIR circuit CH432 (BN/GN) for a short to voltage. TEST the system for normal operation.
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J4 CHECK THE A/C COMPRESSOR OPERATION
- With the A/C cycling switch still disconnected, engine running and the A/C button OFF:
- (EMTC systems) Select PANEL mode.
- (DATC systems) Press the PANEL override button.
- Does the A/C compressor operate?
Yes
GO to J5.
No
INSTALL a new A/C cycling switch. TEST the system for normal operation.
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J5 CHECK FOR VOLTAGE TO THE A/C COMPRESSOR CLUTCH FIELD COIL
- Ignition OFF.
- Disconnect: A/C Compressor Clutch Field Coil C100.
- Start the engine.
- With the engine running, measure the voltage between A/C compressor clutch field coil C100-1, circuit CH401 (VT/WH), harness side and ground.
- Is any voltage present?
Yes
CARRY OUT the A/C clutch relay component test.
CHECK the A/C clutch diode. INSTALL a new diode if necessary. If the relay tests OK, REPAIR circuit CH401 (VT/WH) for a short to voltage. TEST the system for normal operation.
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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J6 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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