Pinpoint Test M: The Air Conditioning (A/C) Is Always On - A/C Compressor Does Not Cycle
Climate Control System
Pinpoint Tests
Pinpoint Test M: 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, in the Dual Automatic Temperature Control (DATC) system, a message is sent 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; or in the Electronic Manual Temperature Control (EMTC) system, voltage is sent to the IC through circuit CH434 (GY/YE), then a message is sent from the IC through the HS-CAN bus to the PCM.
Voltage is provided to the A/C clutch relay switch contacts. When the PCM energizes the relay, voltage is supplied to the A/C compressor clutch field coil. The A/C compressor clutch field coil is grounded.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- PCM
- A/C evaporator temperature sensor
- A/C pressure transducer
- A/C control relay
- A/C compressor
PINPOINT TEST M: THE AIR CONDITIONING (A/C) IS ALWAYS ON - A/C COMPRESSOR DOES NOT CYCLE
-------------------------------------------------
M1 CHECK THE A/C PRESSURE SENSOR (ACP_PSI) PCM PID
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: A/C Pressure PCM PID.
- With the manifold gauge set connected, compare the pressure readings of the manifold gauge set and the ACP_PSI PID.
- Are the pressure values of the manifold gauge set and the ACP_PSI PCM PID similar?
Yes
GO to M2.
No
INSTALL a new A/C pressure transducer. TEST the system for normal operation.
-------------------------------------------------
M2 CHECK THE POST EVAPORATOR TEMPERATURE SENSOR INPUT (PEVAP_TMP) HVAC PID
- Allow the vehicle exterior and interior to stabilize to an ambient temperature above 16°C (60°F).
- Enter the following diagnostic mode on the scan tool: PEVAP_TMP HVAC PID.
- Does the PEVAP_TMP HVAC PID read similar to the ambient temperature?
Yes
GO to M3.
No
CARRY OUT the Evaporator Temperature Sensor component test Evaporator Temperature Sensor. If the sensor tests OK, GO to M6. If the sensor does not test OK, INSTALL a new heater core and evaporator core housing. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
-------------------------------------------------
M3 CHECK THE AIR CONDITIONING CLUTCH (WAC_ACCR) PCM PID WITH THE A/C OFF
- Enter the following diagnostic mode on the scan tool: WAC_ACCR PCM PID.
- Select the OFF position on the HVAC module.
- Does the WAC_ACCR PCM PID read ON?
Yes
GO to M6.
No
GO to M4.
-------------------------------------------------
M4 CHECK FOR VOLTAGE TO THE A/C COMPRESSOR CLUTCH FIELD COIL
- Ignition OFF.
- Disconnect: A/C Compressor Clutch Field Coil C100.
- Ignition ON.
- Select the OFF position on the HVAC module.
- 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
GO to M5.
No
INSTALL a new A/C compressor. TEST the system for normal operation.
-------------------------------------------------
M5 CHECK CIRCUIT CH401 (VT/WH) FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- 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
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.
-------------------------------------------------
M6 CHECK THE PCM CONNECTION
- Disconnect all the PCM connectors.
- Inspect the module connectors for:
- corrosion.
- pushed-out terminals.
- damaged terminals.
- Connect and correctly seat all the PCM connectors.
- Clear the DTCs.
- 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.
-------------------------------------------------