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Diagnostic Test

WARNING: This page is about a different car, the 2005 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
  1. 1)  CHECK THE BLOWER SPEED SETTING 

    Was the blower control set to high speed for the entire Cooldown Test? 

    Yes 

    1. Go To step  2).

    No 

    1. Start the engine, set the blower control to high speed, and then run the Cooldown Test again.
    2. Perform BODY VERIFICATION TEST - VER 1 .
  2. 2)  CHECK THE (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR A SHORT TO THE (C121) SENSOR GROUND CIRCUIT 
    Fig 1: Checking Blower Switch Position Signal Circuit For Short To Sensor Ground Circuit
    GC0028173Courtesy of DAIMLERCHRYSLER CORP.

    Turn the ignition off.

    Disconnect the A/C Heater Control C2 harness connector.

    Measure the resistance between the (C41) Blower Switch Position Signal circuit and the (C121) Sensor Ground circuit in the A/C Heater Control C2 harness connector.

    Is the resistance below 10K ohms? 

    Yes  

    1. Repair the (C41) Blower Switch Position Signal circuit for a short to the (C121) Sensor Ground circuit. Run the Cooldown Test again after the repair is complete.
    2. Perform BODY VERIFICATION TEST - VER 1 .

    No 

    1. Go To step  3).
  3. 3)  CHECK THE (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT VOLTAGE 
    Fig 2: Checking Blower Switch Position Signal Circuit Voltage
    GC0028174Courtesy of DAIMLERCHRYSLER CORP.

    Reconnect the A/C Heater Control C2 harness connector.

    Disconnect the A/C Heater Control C3 harness connector.

    Turn the ignition on.

    Measure the voltage of the (C41) Blower Switch Position Signal circuit.

    Is the voltage above 4.8 volts? 

    Yes 

    1. Check the blower motor and related circuits for the cause of blower operation problems and repair as necessary. Run the Cooldown Test again after the repair is complete.
    2. Perform BODY VERIFICATION TEST - VER 1 .

    No 

    1. Go To step  4).
  4. 4)  CHECK THE (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR A SHORT TO GROUND 
    Fig 3: Checking Blower Switch Position Signal Circuit For Short To Ground
    GC0028175Courtesy of DAIMLERCHRYSLER CORP.

    Turn the ignition off.

    Disconnect the A/C Heater Control C2 harness connector.

    Measure the resistance of the (C41) Blower Switch Position Signal circuit between ground and the A/C Heater Control C3 harness connector.

    Is the resistance below 10K ohms? 

    Yes  

    1. Repair the (C41) Blower Switch Position Signal circuit for a short to ground. Run the Cooldown Test again after the repair is complete.
    2. Perform BODY VERIFICATION TEST - VER 1 .

    No 

    1. Go To step  5).
  5. 5)  CHECK (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR AN OPEN 
    Fig 4: Checking Blower Switch Position Signal Circuit For Open
    GC0028176Courtesy of DAIMLERCHRYSLER CORP.

    Measure the resistance of the (C41) Blower Switch Position Signal circuit between the A/C Heater Control C2 harness connector and the A/C Heater Control C3 harness connector.

    Is the resistance below 5.0 ohms? 

    Yes 

    1. Replace the A/C Heater Control in accordance with the Service Information. Run the Cooldown Test again after the repair is complete.
    2. Perform BODY VERIFICATION TEST - VER 1 .

    No 

    1. Repair the (C41) Blower Switch Position Signal circuit for an open. Run the Cooldown Test again after the repair is complete.
    2. Perform BODY VERIFICATION TEST - VER 1 .
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