Pinpoint Test I: The Air Conditioning (A/C) is Always On - A/C Compressor Does Not Cycle
Climate Control System
Pinpoint Test I: The Air Conditioning (A/C) is Always On - A/C Compressor Does Not Cycle
Refer to Wiring Diagrams Set 54, Manual Climate Control System for schematic and connector information. Electrical Diagrams
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 (Generic Electronic Module). When the A/C cycling switch opens (low pressure) it removes the ground to the GEM (Generic Electronic Module). The GEM (Generic Electronic Module) sends this status to the IC (Instrument Cluster) through the MS-CAN (Medium Speed Controller Area Network), then from the IC (Instrument Cluster) to the PCM through the HS-CAN (High Speed Controller Area Network). 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.
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.
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.
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.
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 . TEST the system for normal operation.