Pinpoint Test I: The Air Conditioning (A/C) Is Always On - A/C Compressor Does Not Cycle
Climate Control System
Pinpoint Tests
Pinpoint Test I: 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
Normal Operation
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 normally closed (sufficient pressure) and supplies ground to the GEM. When the A/C cycling switch opens (low pressure) it removes the ground to the GEM. The GEM sends this status to the IC through the MS-CAN, then from the IC to the PCM through the HS-CAN. This tells the PCM to turn on the A/C compressor when pressures are high enough and off the A/C compressor before the refrigerant pressure is low enough to make the evaporator temperatures cold enough to freeze the condensation.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- A/C cycling switch
- A/C control relay
- A/C clutch air gap
- A/C diode
PINPOINT TEST I: THE AIR CONDITIONING (A/C) IS ALWAYS ON - A/C COMPRESSOR DOES NOT CYCLE
NOTE: Before carrying out the following test, diagnose any PCM, Generic Electronic Module (GEM) or Instrument Cluster (IC) DTCs.
NOTE: Before carrying out the following test, check that the A/C system pressure is above 290 kPa (42 psi). If the pressure is below 290 kPa (42 psi), refer to Fluorescent Dye Leak Detection Fluorescent Dye Leak Detection.
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I1 CHECK THE A/C LOW PRESSURE CYCLING SWITCH (AC_LOWSW) PCM PID
- Start the engine.
- Enter the following diagnostic mode on the scan tool: PCM DataLogger.
- With the engine running, place the function selector switch in the PANEL position and press the A/C request button and monitor the AC_LOWSW PCM PID.
- Does the AC_LOWSW PCM PID read open?
Yes
GO to I3.
No
GO to I2.
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I2 CHECK THE A/C LOW PRESSURE CYCLING SWITCH (AC_LOWSW) PCM PID WITH THE A/C CYCLING SWITCH DISCONNECTED
- Ignition OFF.
- Disconnect: A/C Cycling Switch C1081.
- Start the engine.
- Enter the following diagnostic mode on the scan tool: PCM DataLogger.
- With the engine running, place the function selector switch in the PANEL position and press the A/C request button and monitor the AC_LOWSW PCM PID.
- Does the AC_LOWSW PCM PID read open?
Yes
INSTALL a new A/C cycling switch . TEST the system for normal operation.
No
REPAIR circuit 7-FA11 (YE) for a short to ground. TEST the system for normal operation.
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I3 CHECK THE A/C RELAY
- Ignition OFF.
- Disconnect: A/C Control Relay .
- Start the engine.
- With the engine running, place the function selector switch in the PANEL position.
- Is the A/C compressor clutch disengaged?
Yes
INSTALL a new A/C clutch relay. CHECK the A/C clutch diode. INSTALL a new diode if necessary. TEST the system for normal operation.
No
GO to I4.
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I4 CHECK FOR VOLTAGE AT THE A/C COMPRESSOR CLUTCH FIELD COIL
- Ignition OFF.
- Disconnect: A/C Compressor Clutch Field Coil C100 .
- Ignition ON.
- Measure the voltage between A/C compressor clutch field coil C100-1, circuit 15S-FA6 (GN/YE), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
REPAIR circuit 15S-FA6 (GN/YE) 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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