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Home >> Mercury >> 2011 >> Grand Marquis V8-4.6L Flex Fuel >> Repair and Diagnosis >> Heating and Air Conditioning >> Testing and Inspection >> Pinpoint Tests >> Pinpoint Test K: The Air Conditioning (A/C) Is Inoperative

Pinpoint Test K: The Air Conditioning (A/C) Is Inoperative




Climate Control System

Pinpoint Tests

Pinpoint Test K: The Air Conditioning (A/C) is Inoperative

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, the climate control assembly or HVAC module sends voltage to the A/C cycling switch. The PCM receives input from the A/C cycling switch, when closed (sufficient pressure). The A/C cycling switch is used for A/C compressor cycling. The switch is used by the PCM to turn off the A/C compressor before the line pressures are low enough to drop the evaporator temperature excessively low and freeze the condensation.

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.

When an A/C request is received by the PCM, the A/C compressor clutch will only be engaged through the A/C clutch relay 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 low refrigerant pressure from the A/C cycling switch.
- The PCM does not detect excessively high engine coolant temperature.
- The PCM does not detect an ambient air temperature too low.
- The PCM has not detected a Wide Open Throttle (WOT) condition.

This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Wiring, terminals or connectors
- A/C pressure transducer
- PCM
- A/C clutch relay
- Function selector switch
- HVAC module
- A/C cycling switch
- A/C compressor clutch field coil
- A/C clutch air gap

PINPOINT TEST K: THE AIR CONDITIONING (A/C) IS INOPERATIVE

NOTE: Some PCM DTCs may inhibit A/C operation. If any PCM DTCs are retrieved, diagnose those first. Refer to the PCM DTC Chart. PCM DTC Chart

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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K1 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 PID.
- Are the pressure values of the manifold gauge set and the ACP_PRESS PID similar?

Yes
GO to K2.

No
INSTALL a new A/C pressure transducer. TEST the system for normal operation.

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K2 CHECK THE AIR CONDITIONING CYCLING SWITCH (ACCS) PCM PID WITH THE A/C ON


- Enter the following diagnostic mode on the scan tool: ACCS PCM PID.
- Place the function selector switch in the MAX A/C position or press the PANEL and A/C manual override buttons on the HVAC module.
- Does the PCM PID ACCS read ON?

Yes
GO to K3.

No
GO to K4.

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K3 CHECK THE AIR CONDITIONING CLUTCH (WAC/ACCR) PCM PID WITH THE A/C ON


- Enter the following diagnostic mode on the scan tool: WAC/ACCR PCM PID.
- Does the WAC/ACCR PCM PID read ON?

Yes
GO to K9.

No
GO to K13.

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K4 CHECK A/C CYCLING SWITCH VOLTAGE


- Ignition OFF.
- Disconnect: A/C Cycling Switch C1081.
- Ignition ON.
- Measure the voltage between the A/C cycling switch C1081-4, circuit 348 (VT), harness side and ground.




- Is the voltage greater than 10 volts?

Yes
GO to K7.

No
GO to K5.

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K5 CHECK CIRCUIT 348 (VT) FOR AN OPEN


- Ignition OFF.
- Disconnect: Function Selector Switch C294A or HVAC Module C228B.

- NOTE: Manual climate control systems only.

- Measure the resistance between selector switch C294A-2, circuit 348 (VT), harness side and A/C cycling switch C1081-4, circuit 348 (VT), harness side.





- NOTE: EATC systems only.

- Measure the resistance between A/C cycling switch C1081-4, circuit 348 (VT), harness side and HVAC module C228B-11, circuit 348 (VT), harness side.




- Is the resistance less than 5 ohms?

Yes
Manual climate control systems, GO to K6.

Electronic Automatic Temperature Control (EATC) systems, GO to K14.

No
REPAIR circuit 348 (VT) for an open. TEST the system for normal operation.

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K6 CHECK CIRCUIT 1040 (RD/BK) FOR VOLTAGE


- Disconnect: Function Selector Switch C294A.
- Ignition ON.
- Measure the voltage between ground and function selector switch C294A-4, circuit 1040 (RD/BK), harness side.




- Is the voltage greater than 10 volts?

Yes
INSTALL a new function selector switch. TEST the system for normal operation.

No
VERIFY the Central Junction Box (CJB) fuse 17 (10A) is OK. If OK, REPAIR circuit 1040 (RD/BK) for an open. TEST the system for normal operation.

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K7 CHECK A/C CYCLING SWITCH


- Ignition OFF.
- Measure the resistance between the A/C cycling switch terminals.




- Is the resistance less than 21 ohms?

Yes
GO to K8.

No
INSTALL a new A/C cycling switch. TEST the system for normal operation.

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K8 CHECK CIRCUIT 883 (PK/LB) FOR AN OPEN


- Disconnect: PCM C175B.
- Measure the resistance between A/C cycling switch C1081-1, circuit 883 (PK/LB), harness side and PCM C175B-15, circuit 883 (PK/LB), harness side.




- Is the resistance less than 5 ohms?

Yes
GO to K13.

No
REPAIR circuit 883 (PK/LB) for an open. TEST the system for normal operation.

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K9 CHECK THE VOLTAGE AT THE A/C COMPRESSOR CLUTCH FIELD COIL


- Ignition OFF.
- Disconnect: A/C Compressor Clutch Field Coil C100.
- Ignition ON.
- Start the engine.
- With the engine running, measure the voltage between A/C compressor clutch field coil C100-1, circuit 321 (GY/WH), harness side and ground.




- Is the voltage greater than 10 volts?

Yes
GO to K10.

No
INSTALL a known good A/C relay. TEST the system for normal operation. If the condition remains, GO to K12.

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K10 CHECK THE GROUND AT THE A/C COMPRESSOR CLUTCH FIELD COIL


- With the engine running, measure the voltage between A/C compressor clutch field coil C100-2, circuit 57 (BK), harness side and A/C compressor clutch field coil C100-1, circuit 321 (GY/WH), harness side.




- Is the voltage greater than 10 volts?

Yes
GO to K11.

No
REPAIR circuit 57 (BK) for an open. TEST the system for normal operation.

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K11 CHECK THE A/C COMPRESSOR CLUTCH AIR GAP


- Ignition OFF.
- 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 greater than 0.026 in (0.65 mm)?

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 field coil. REFER to Climate Control Service and Repair. TEST the system for normal operation.

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K12 CHECK CIRCUIT 1810 (LG/OG) FOR AN OPEN


- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- Ignition ON.
- Measure the voltage between A/C control relay socket pin 5, circuit 1810 (LG/OG) and ground.




- Is the voltage greater than 10 volts?

Yes
REPAIR circuit 321 (GY/WH) for an open. TEST the system for normal operation.

No
VERIFY the BJB fuse 11 (15A) is OK. If OK, REPAIR circuit 1810 (LG/OG) for an open. TEST the system for normal operation.

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K13 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.

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K14 CHECK THE HVAC MODULE CONNECTION


- Inspect the 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. REFER to Climate Control Heating Ventilation Air Conditioning (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.

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