Pinpoint Test K: The Air Conditioning (A/C) is Always On - A/C Compressor Does Not Cycle
Climate Control System
Pinpoint Test K: 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 Electrical Diagrams.
Normal Operation
When A/C is requested the HVAC module grounds a circuit to the Instrument Panel Cluster (IPC). The IPC (Instrument Panel Cluster) then sends an A/C request through the High Speed Controller Area Network (HS-CAN) to the PCM.
Voltage is provided to the A/C clutch relay coil and switch contacts. When A/C is requested and A/C line pressures allow, a ground is provided to the A/C clutch relay coil from the PCM, energizing the A/C clutch relay. 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 evaporator discharge air temperature sensor is used for A/C compressor cycling. An accurate evaporator temperature is critical for compressor engagement. The PCM uses the temperature measurement to turn the A/C compressor off before the evaporator temperature is cold enough to freeze the condensation on the evaporator core.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- PCM
- IPC (Instrument Panel Cluster)
- Evaporator discharge air temperature sensor
- A/C clutch relay
- A/C compressor clutch air gap
PINPOINT TEST K : THE AIR CONDITIONING (A/C) IS ALWAYS ON - A/C COMPRESSOR DOES NOT CYCLE
K1 CHECK THE A/C EVAPORATOR TEMPERATURE (EVAP_TEMP) Instrument Panel Cluster (IPC) PID
- Ignition ON.
- Allow the vehicle exterior and interior to stabilize to the ambient temperature.
- Enter the following diagnostic mode on the scan tool: IPC (Instrument Panel Cluster) DataLogger.
- Monitor the EVAP_TEMP IPC (Instrument Panel Cluster) PID
Does the EVAP_TEMP IPC (Instrument Panel Cluster) PID read similar to the ambient temperature?
Yes
GO to K2.
No
GO to K8.
K2 CHECK AIR CONDITIONING COMPRESSOR COMMANDED STATE (ACC_CMD) PCM PID WITH THE A/C OFF
- Enter the following diagnostic mode on the scan tool: PCM DataLogger.
- Select PANEL and press the A/C button (indicator off) on the HVAC controls.
- Monitor the ACC_CMD PCM PID
Does the ACC_CMD PCM PID read OFF?
Yes
GO to K3.
No
GO to K10.
K3 CHECK THE A/C RELAY
- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- Start the engine.
- OBSERVE A/C compressor clutch operation.
Does the A/C compressor clutch disengage?
Yes
GO to K4.
No
GO to K6.
K4 CHECK THE A/C CLUTCH RELAY
NOTICE: The following step uses a test light to simulate normal circuit loads. Use only the test light recommended in the Special Tools table at the beginning or equivalent. To avoid connector terminal damage, use the Flex Probe Kit for the test light probe connection to the vehicle. Do not use the test light probe directly on any connector.
- Connect a 12-volt test light between A/C clutch relay socket pin 1, circuit CBP02 (GN) and A/C clutch relay socket pin 2, circuit CH302 (WH/BN).
Does the test light illuminate?
Yes
GO to K5.
No
INSTALL a new A/C clutch relay. TEST the system for normal operation.
K5 CHECK THE A/C CLUTCH RELAY COIL SWITCHED GROUND CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: PCM C175B.
- Measure the resistance between ground and PCM C175B-25, circuit CH302 (WH/BN), harness side.
Is the resistance greater than 10,000 ohms?
Yes
GO to K10.
No
REPAIR circuit CH302 (WH/BN) for a short to ground. TEST the system for normal operation.
K6 CHECK FOR VOLTAGE TO 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 CH401 (VT/WH), harness side and ground.
Is any voltage present?
Yes
REPAIR circuit CH401 (VT/WH) for a short to voltage. TEST the system for normal operation.
No
GO to K7.
K7 CHECK THE A/C COMPRESSOR CLUTCH AIR GAP
- Measure the A/C compressor clutch air gap at 3 equally spaced locations between the clutch hub and the A/C compressor clutch pulley.
Is the A/C compressor clutch air gap average less than 0.3 mm (0.012 in)?
Yes
ADJUST the A/C compressor clutch gap. REFER to Air Conditioning (A/C) Clutch Air Gap Adjustment Adjustments. TEST the system for normal operation.
No
INSTALL a new A/C compressor clutch. TEST the system for normal operation.
K8 CHECK THE EVAPORATOR TEMPERATURE AIR TEMPERATURE SENSOR
- Ignition OFF.
- Disconnect: Evaporator Discharge Air Temperature Sensor C296.
- CARRY OUT the Evaporator Discharge Air Temperature Sensor component test Component Tests.
Did the evaporator discharge air temperature sensor test OK?
Yes
GO to K9.
No
INSTALL a new evaporator discharge air temperature sensor. TEST the system for normal operation.
K9 CHECK THE IPC (Instrument Panel Cluster) CONNECTION
- Disconnect all the IPC (Instrument Panel Cluster) connectors.
- Inspect the IPC (Instrument Panel Cluster) connectors for:
- corrosion.
- pushed-out terminals.
- damaged terminals.
- Connect and correctly seat all the IPC (Instrument Panel Cluster) connectors.
- Operate the system and verify the concern is still present.
Is the concern still present?
Yes
INSTALL a new IPC (Instrument Panel Cluster). 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. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
K10 CHECK THE PCM CONNECTION
- Disconnect all the PCM connectors.
- Inspect the PCM connectors for:
- corrosion.
- pushed-out terminals.
- damaged terminals.
- Connect and correctly seat all the PCM connectors.
- Operate the system and verify the concern is still present.
Is the concern still present?
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.