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 pressure transducer is used for A/C compressor cycling. The A/C pressure transducer is used by the PCM to turn off the A/C compressor before the refrigerant pressure is either to high or 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
- A/C pressure transducer
- 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 PRESSURE SENSOR (ACP_PRESS) PCM PID
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: ACP_PRESS PCM PID .
- With the manifold gauge set connected, compare the pressure readings of the manifold gauge set and the ACP_PRESS PCM PID.
- Are the pressure values of the manifold gauge set and the ACP_PRESS PCM PID similar?
Yes
GO to I2.
No
INSTALL a new A/C pressure transducer. TEST the system for normal operation.
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I2 CHECK 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 I3.
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I3 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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