Pinpoint Test P: The Air Conditioning (A/C) is Always On
Climate Control System
Pinpoint Tests
Pinpoint Test P: The Air Conditioning (A/C) is Always On
Refer to Wiring Diagram Set 55 (Escape/Mariner, Escape Hybrid/Mariner Hybrid), Automatic Climate Control System for schematic and connector information. Diagrams By Number
When A/C is requested, a message is sent from the HVAC module over the MS-CAN bus to the IC, then from the IC through the HS-CAN bus to the PCM.
When an A/C request is received from the HVAC module, an A/C demand message is sent from the PCM over the HS-CAN bus to the Air Conditioning Compressor Module (ACCM) if all of the following conditions are met:
- The PCM does not detect excessively high or low refrigerant pressure from the A/C pressure transducer.
- The PCM does not detect excessively high engine coolant temperature.
- The PCM does not detect an ambient air temperature below -1°C (30°F).
- The PCM has not detected a Wide Open Throttle (WOT) condition.
- The HVAC module does not detect an evaporator discharge air temperature below 2°C (36°F).
When the ACCM receives the A/C demand message, it will engage. Instead of cycling ON and OFF like a traditional A/C compressor, the PCM monitors the evaporator discharge temperature from the HVAC module to raise or lower the electric A/C compressor speed as required.
This pinpoint test is intended to diagnose the following:
- HVAC module
- Electric A/C compressor
- A/C evaporator discharge temperature sensor
- A/C pressure transducer
PINPOINT TEST P: THE AIR CONDITIONING (A/C) IS ALWAYS ON
NOTE: Diagnose any PCM, HVAC module or ACCM DTCs before carrying out the following pinpoint test.
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P1 CHECK THE A/C EVAPORATOR TEMPERATURE (EVAP_TEMP) HVAC PID
- Allow the vehicle exterior and interior to stabilize to an ambient temperature.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: EVAP_TEMP HVAC PID.
- Does the EVAP_TEMP HVAC PID read similar to the ambient temperature?
Yes
GO to P2.
No
INSTALL a new A/C evaporator discharge temperature sensor. TEST the system for normal operation.
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P2 CHECK THE (A/C) SWITCH (CC_SW_AC) HVAC PID WITH THE A/C OFF
- Start the engine.
- Enter the following diagnostic mode on the scan tool: CC_SW_AC HVAC PID.
- Select PANEL and make sure the A/C indicator is OFF.
- Does the CC_SW_AC HVAC PID read Inactive?
Yes
GO to P3.
No
INSTALL a new HVAC module. REFER to Climate Control Service and Repair. TEST the system for normal operation.
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P3 CHECK THE AIR CONDITIONING COMPRESSOR COMMANDED STATE (ACC_CMD) PCM PID WITH THE A/C OFF
- Enter the following diagnostic mode on the scan tool: ACC_CMD PCM PID.
- Select PANEL and make sure the A/C indicator is OFF.
- Does the ACC_CMD PCM PID read OFF?
Yes
INSTALL a new electric A/C compressor. REFER to Climate Control Service and Repair. TEST the system for normal operation.
No
INSTALL a new PCM. TEST the system for normal operation.
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