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Home >> Ford >> 2000 >> Taurus LX, 3.0 2, AX4N >> Repair and Diagnosis >> External Pages >> Different car >> Section 204 (Engine Controls - Pinpoint Tests - 6.0L Diesel (99P F450/550)) >> Pinpoint Test AV: Air Conditioning (A/C) Relay Control Circuit >> Test Procedure

Test Procedure

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  1. AV1 PRELIMINARY DIAGNOSIS FOR DTC P0645 
    • Carry out a visual inspection.
    • Retrieve and record all DTCs.
    • Clear all DTCs.
    • Carry out the on-demand self test.

    Is DTC P0645 present? 

    Yes No
    GO to  AV2. UNABLE to duplicate the condition. CHECK for a loose connection, and damaged or corroded terminals. WIGGLE the harness attempting to recreate the concern. REPAIR as necessary. REFER to CLIMATE CONTROL SYSTEM - GENERAL INFORMATION for A/C system concerns.
  2. AV2 DIAGNOSTIC TROUBLE CODE (DTC) P0645 
    • Possible causes:
    • A/C clutch relay control circuit shorted to voltage
    • A/C clutch relay control circuit open
    • A/C clutch relay control circuit shorted to ground
    • A/C clutch relay circuit
    • A/C clutch relay
    • PCM
    • Key ON, engine OFF.
    • Access the ACCS PID.
    • Cycle the A/C control switch OFF and ON.

    Does the ACCS PID indicate ON with the A/C control switch ON and OFF with the A/C control switch OFF? 

    Yes No
    GO to  AV3. REFER to CLIMATE CONTROL SYSTEM - GENERAL INFORMATION to continue diagnosis of the A/C system.
  3. AV3 CHECK THE A/C CLUTCH RELAY COIL POWER CIRCUIT FOR VOLTAGE 
    NOTE: Refer to SYSTEM WIRING DIAGRAMS for the A/C clutch relay coil pin locations.
    • Key OFF.
    • Disconnect the A/C relay.
    • Key ON, engine OFF.
    • Measure the voltage between the A/C clutch relay coil power circuit, harness side and ground.

    Is the voltage greater than 10 volts? 

    Yes No
    GO to  AV4. REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
  4. AV4 CHECK THE A/C CLUTCH RELAY CONTROL CIRCUIT 
    • Connect a test lamp between the A/C clutch relay coil power circuit, harness side and the A/C clutch relay control circuit, harness side.
    • Key ON, engine running.
    • Cycle the A/C control switch OFF and ON.

    Is the test lamp illuminated with the A/C control switch ON and is the test lamp off with the A/C control switch OFF? 

    Yes No
    REFER to CLIMATE CONTROL SYSTEM - GENERAL INFORMATION to continue diagnosis of the A/C system. GO to  AV5.
  5. AV5 CHECK THE A/C CLUTCH RELAY CONTROL CIRCUIT FOR A SHORT TO VOLTAGE 
    • Key OFF.
    • Disconnect the PCM body harness connector.
    • Key ON, engine OFF.
    • Measure the voltage between the PCM body harness connector pin 2, harness side and ground.

    Is the voltage less than 0.2 volts? 

    Yes No
    GO to  AV6. REPAIR the relay control circuit. CLEAR the DTCs. REPEAT the self-test.
  6. AV6 CHECK THE A/C CLUTCH RELAY CONTROL CIRCUIT FOR A SHORT TO GROUND 
    • Key OFF.
    • Measure the resistance between the PCM body harness connector pin 2, harness side and ground.

    Is the resistance greater than 10,000 ohms? 

    Yes No
    GO to  AV7. REPAIR the short to ground. CLEAR the DTCs. REPEAT the self-test.
  7. AV7 CHECK THE A/C CLUTCH RELAY CONTROL CIRCUIT FOR AN OPEN 
    • Measure the resistance between the PCM body harness connector pin 2, harness side and the A/C relay clutch control circuit harness side.

    Is the resistance less than 5 ohms? 

    Yes No
    INSTALL a new PCM. CLEAR the DTCs. REPEAT the self-test. REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
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