Pinpoint Test N: The Air Conditioning (A/C) is Always On - A/C Compressor Does Not Cycle
Climate Control System
Pinpoint Test N: 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. [1][2]Diagrams By Number
Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information. [1][2]Diagrams By Number
Normal Operation
Under normal operation, for Fusion equipped with navigation and all MKZ vehicles, when A/C button is pressed, a message is sent from the Front Controls Interface Module (FCIM) over the Medium Speed Controller Area Network (MS-CAN) bus to the HVAC module. The HVAC module then sends an A/C request message over the MS-CAN (Medium Speed Controller Area Network) bus to the Instrument Cluster (IC) , then from the IC (Instrument Cluster) through the High Speed Controller Area Network (HS-CAN) bus to the PCM.
For all vehicles equipped with navigation, when MAX A/C is selected on the touch screen, the Audio Control Module (ACM) sends a message over the MS-CAN (Medium Speed Controller Area Network) bus to the HVAC module that MAX A/C has been selected.
For Fusion not equipped with navigation, when A/C is requested, a message is sent over the MS-CAN (Medium Speed Controller Area Network) bus to the IC (Instrument Cluster) , then from the IC (Instrument Cluster) through the HS-CAN (High Speed Controller Area Network) bus to the PCM.
Ignition voltage is provided to the A/C clutch relay switch through circuit SBB25 (RD). When the PCM energizes the relay, ignition voltage is supplied to the A/C clutch through circuit CH401 (VT/WH). Ground is supplied for the A/C clutch through circuit GD121 (BK/YE).
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- PCM
- evaporator discharge air temperature sensor
- A/C control relay
- A/C clutch air gap
- Evaporator core seals
PINPOINT TEST N : THE AIR CONDITIONING (A/C) IS ALWAYS ON - A/C COMPRESSOR DOES NOT CYCLE
N1 CHECK THE A/C EVAPORATOR TEMPERATURE (EVAP_TEMP) HVAC PID
NOTE: Before carrying out the following test, diagnose any HVAC, PCM or Instrument Cluster (IC) DTCs.
NOTE: CHECK On-Line Automotive Service Information System (OASIS) for any applicable Technical Service Bulletins (TSBs). If a Technical Service Bulletin (TSB) exists for this concern, discontinue this test and follow the TSB (Technical Service Bulletin) instructions. If no TSBs (Technical Service Bulletins) address this concern, continue with this test.
- Ignition ON.
- Allow the vehicle exterior and interior to stabilize to an ambient temperature between 15°C (60°F) and 32°C (90°F).
- 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 N3.
No
GO to N2.
N2 CHECK THE EVAPORATOR DISCHARGE AIR TEMPERATURE SENSOR RESISTANCE
- Ignition OFF.
- Disconnect: For Electronic Manual Temperature Control (EMTC) Systems, Inline C211.
- Disconnect: For Dual Automatic Temperature Control (DATC) Systems, Inline C213.
- Measure the resistance between:
- For EMTC (Electronic Manual Temperature Control) Systems, inline C211-13, circuit VH406 (VT/BN), HVAC case harness side and inline C211-15, circuit RH111 (GY/BU), HVAC case harness side.
- For DATC (Dual Automatic Temperature Control) Systems, inline C213-13, circuit VH406 (VT/BN), HVAC case harness side and inline C213-15, circuit RH111 (GY/BU), HVAC case harness side.
- Compare the measurement to the chart and table of the Evaporator Discharge Air Temperature Sensor component test.
Is the resistance within the specified values for the temperatures?
Yes
GO to N9.
No
INSTALL a new evaporator discharge air temperature sensor. TEST the system for normal operation.
N3 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.
Does the ACC_CMD PCM PID read ON?
Yes
GO to N8.
No
GO to N4.
N4 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-B, circuit CH401 (VT/WH), harness side and ground.
Is the voltage greater than 10 volts?
Yes
GO to N5.
No
ADJUST the A/C compressor clutch gap. REFER to Air Conditioning (A/C) Clutch Air Gap Adjustment . TEST the system for normal operation.
N5 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-B, circuit CH401 (VT/WH), harness side and ground.
Is the voltage greater than 10 volts?
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. TEST the system for normal operation. If the concern is still present, GO to N6.
N6 CHECK THE EVAPORATOR DISCHARGE AIR TEMPERATURE SENSOR MOUNTING
- Remove the instrument panel.
- Inspect the evaporator discharge air temperature sensor for:
- damage.
- correct mounting.
- damaged mounting tabs.
Is the sensor and mounting correct and free of damage?
Yes
GO to N7.
No
INSTALL a new evaporator discharge air temperature sensor. TEST the system for normal operation.
N7 CHECK THE EVAPORATOR CORE SEALS
- Remove the heater core and evaporator core housing.
- Remove the evaporator core.
- Inspect the evaporator core seals for:
- misalignment.
- damage.
- loose fit.
Is the evaporator seal mounting tight, correct and free of damage?
Yes
GO to N9.
No
CORRECT the evaporator core seal alignment or INSTALL a new evaporator core. TEST the system for normal operation.
N8 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.
N9 CHECK THE HVAC MODULE CONNECTION
- Inspect the HVAC module connectors for:
- corrosion.
- pushed-out terminals.
- damaged terminals.
- Connect and correctly seat all the HVAC module connectors.
- Clear the DTCs.
- Operate the system and verify the concern is still present.
Is the concern still present?
Yes
INSTALL a new HVAC module. 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.