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Home >> Mercury >> 2009 >> Milan FWD V6-3.0L >> Repair and Diagnosis >> Heating and Air Conditioning >> Testing and Inspection >> Pinpoint Tests >> Pinpoint Test M: The Air Conditioning (A/C) Is Inoperative

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




Climate Control System

Pinpoint Tests

Pinpoint Test M: 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, in Electronic Automatic Temperature Control (EATC) or 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 a 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 in Electronic Manual Temperature Control (EMTC) systems.

Ignition voltage for the A/C clutch relay switch is provided 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:
- Fuse
- Wiring, terminals or connectors
- PCM
- HVAC module - EATC
- HVAC module - DATC
- HVAC module - EMTC
- A/C evaporator discharge temperature sensor
- A/C pressure transducer
- A/C compressor clutch field coil
- A/C control relay
- A/C clutch air gap



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

NOTICE: It is important to install relays in their correct position in the Battery Junction Box (BJB). Installing a relay incorrectly may cause wiring shorts or damage to modules. While carrying out diagnostics on BJB relays, have only one BJB relay removed at a time. Failure to follow these instructions may result in damage to the vehicle circuitry or to control modules.

NOTE: Some PCM DTCs may inhibit A/C operation. If any PCM DTCs are retrieved, diagnose those first. Refer to Computers and Control Systems Information.

NOTE: When disconnecting and reconnecting the pressure transducer electrical connector, make sure that the connector-locking device is in place and that the locking device and connector are correctly and fully seated.

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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M1 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 R-134a Manifold Gauge Set connected, compare the pressure readings of the R-134a Manifold Gauge Set and the ACP_PRESS PCM PID.
- Are the pressure values of the R-134a Manifold Gauge Set and the ACP_PRESS PCM PID similar?

Yes
GO to M2.

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

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M2 CHECK THE A/C EVAPORATOR TEMPERATURE (EVAP_TEMP) HVAC PID (3.5L ONLY) OR EVAPORATOR TEMPERATURE (A/CT) PCM 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: EVAP_TEMP HVAC PID (3.5L only) or A/CT PCM PID.
- Does the EVAP_TEMP HVAC PID (3.5L ONLY) or A/CT PCM PID read similar to the ambient temperature?

Yes
DATC/EATC, GO to M3.

EMTC, GO to M4.

No
INSTALL a new A/C evaporator discharge temperature sensor. TEST the system for normal operation.

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M3 CHECK THE AIR CONDITIONING SWITCH STATUS (CC_AC) HVAC PID WITH THE A/C ON


- Enter the following diagnostic mode on the scan tool: CC_AC HVAC PID.
- Press and hold the A/C manual override button on the HVAC module - DATC or HVAC module - EATC module.
- Does the CC_AC HVAC PID read DEPRESSED?

Yes
GO to M5.

No
GO to M14.

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M4 CHECK THE EMTC A/C SIGNAL WITH THE A/C ON


- Ignition OFF.
- Disconnect: IC C220.
- Ignition ON.
- Select panel mode and press the A/C button on the HVAC module - EMTC.
- Measure the resistance between IC C220-23, circuit CH434 (GY/YE), harness side and ground.




- Is the resistance less than 5 ohms?

Yes
GO to M5.

No
GO to M7.

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M5 CHECK THE AIR CONDITIONING COMPRESSOR CYCLING SWITCH (ACCS) PCM PID WITH THE A/C ON


- Ignition OFF.
- NOTE: For EMTC systems only.
- Disconnect: For EMTC systems only, IC C220.
- Ignition ON.
- NOTE: For EMTC systems only.
- Enter the following diagnostic mode on the scan tool: ACCS PCM PID.
- Press the PANEL and A/C manual override buttons on the HVAC module - DATC and HVAC module - EATC or select MAX A/C on the HVAC module - EMTC.
- Does the ACCS PCM PID read ON?

Yes
GO to M6.

No
GO to M15.

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M6 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 M9.

No
GO to M15.

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M7 CHECK CIRCUIT CH434 (GY/YE) FOR AN OPEN


- Ignition OFF.
- Disconnect: HVAC Module - EMTC C2357a .
- Measure the resistance between HVAC module - EMTC C2357a-3, circuit CH434 (GY/YE), harness side and IC C220-23, circuit CH434 (GY/YE), harness side.




- Is the resistance less than 5 ohms?

Yes
GO to M8.

No
REPAIR circuit CH434 (GY/YE) for an open. TEST the system for normal operation.

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M8 CHECK CIRCUIT CH434 (GY/YE) FOR A SHORT TO VOLTAGE


- Ignition ON.
- Measure the voltage between HVAC module - EMTC C2357a-3, circuit CH434 (GY/YE), harness side and ground.




- Is any voltage present?

Yes
REPAIR circuit CH434 (GY/YE) for a short to voltage. TEST the system for normal operation.

No
GO to M15.

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M9 CHECK THE VOLTAGE AT THE A/C COMPRESSOR CLUTCH FIELD COIL


- Ignition OFF.
- Disconnect: A/C Compressor Clutch Field Coil C100.
- Ignition ON.
- Press the PANEL and A/C manual override buttons on the HVAC module - EATC and HVAC module - DATC or select MAX A/C on the HVAC module - EMTC.
- 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 M10.

No
GO to M12.

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M10 CHECK THE GROUND AT THE A/C COMPRESSOR CLUTCH FIELD COIL


- Ignition OFF.
- Measure the resistance between A/C compressor clutch field coil C100-A, circuit GD121 (BK/YE), harness side and ground.




- Is the resistance less than 5 ohms?

Yes
GO to M11.

No
REPAIR circuit GD121 (BK/YE) for an open. TEST the system for normal operation.

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M11 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 greater than 0.6 mm (0.024 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 field coil. TEST the system for normal operation.

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M12 CHECK CIRCUIT SBB25 (RD) FOR VOLTAGE


- Ignition OFF.
- Disconnect: A/C Clutch Relay.
- Ignition ON.
- Measure the voltage between A/C clutch relay socket, circuit SBB25 (RD) and ground.




- Is the voltage greater than 10 volts?

Yes
GO to M13.

No
VERIFY Battery Junction Box (BJB) fuse 25 (10A) is OK. If OK, REPAIR circuit SBB25 (RD) for an open. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short.

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M13 CHECK CIRCUIT CH401 (VT/WH) FOR AN OPEN


- Ignition OFF.
- Measure the resistance between A/C clutch relay socket pin 5, circuit CH401 (VT/WH) and A/C compressor clutch field coil C100-B, circuit CH401 (VT/WH), harness side.




- Is the resistance less than 5 ohms?

Yes
GO to M15.

No
REPAIR circuit CH401 (VT/WH) for an open. TEST the system for normal operation.

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M14 CHECK THE MODULE CONNECTION


- Carry out the HVAC Module Cold Boot Process. HVAC Module Cold Boot Process
- NOTE: DATC/EATC systems only.
- Carry out the HVAC Module - Electronic Automatic Temperature Control (EATC) and HVAC Module - Dual Automatic Temperature Control (DATC) On-Demand Self Test.
- Operate the system.
- Does the concern return?

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. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

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M15 CHECK THE PCM CONNECTION


- Check the DTCs.
- Disconnect all the PCM connectors.
- Check for:
- corrosion.
- pushed-out pins.
- incorrectly seated connector.
- Connect and correctly seat all the PCM connectors.
- Operate the system.
- Does the concern return?

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 cause by a loose or corroded connector.

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