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Home >> Chrysler >> 2004 >> Pacifica AWD >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Body Diagnostic Procedures - HVAC, Ignition Power Accessory, Instrument Cluster, Interior Lighting, Navigation, Overhead Console, Power Door Locks/RKE >> Heating & A/C >> Symptom: *REAR BOOSTER FAN RUNS AT ONLY ONE SPEED >> Diagnostic Procedure

Diagnostic Procedure

*REAR BOOSTER FAN RUNS AT ONLY ONE SPEED - DIAGNOSTIC PROCEDURE

TEST ACTION APPLICABILITY
1 Turn the ignition on.
Press the ATC's PWR switch on.
Press the REAR fan mode switch on, so that it is in manual mode. The word "REAR" should display on the ATC display panel. The word "AUTO" should not be displayed.
Turn the Rear Booster Fan Rear Control switch to AUTO for 30 seconds, then slowly turn it from AUTO to high speed and then back to AUTO.
With the DRBIII®, read the active ATC DTCs.
Does the DRBIII® display any DTCs?
  1. Yes: Return to the Heating & A/C SYMPTOM LIST and choose the symptom(s).

    Perform BODY VERIFICATION TEST VER-1 .

  2. No: Go To 2
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2 Turn the ignition off.
Disconnect the Rear Booster Fan Power Module C1 harness connector.
Disconnect the ATC C1 harness connector.
Measure the resistance between ground and the Rear Booster Fan Control circuit.
Is the resistance below 10K ohms?
  1. Yes: Repair the Rear Booster Fan Control circuit for a short to ground.

    Perform BODY VERIFICATION TEST VER-1 .

  2. No: Go To 3
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3 Turn the ignition off.
Reconnect all previously disconnected components.
Connect the DRBIII® X10 Scope Probe CH7061 to the DRBIII®.
Select the following from the DRBIII® menu: PEP Module Tools; Lab Scope; Live Data; and Lab Scope.
Set the time to 10ms/Div.
Set the voltage range to +20.0v.
Set the offset to 4.00v.
Set the Probe to X10.
Start the engine.
Press the ATC's PWR switch on.
Press the REAR fan mode switch on, so that it is in manual mode. The word "REAR" should display on the ATC display panel. The word "AUTO" should not be displayed.
Using the X10 Scope Probe, back probe the Rear Booster Fan Control circuit in the ATC C1 harness connector.
NOTE: The RR Booster Fan Power Module provides a 12.0v signal to the ATC over the Rear Booster Fan Control circuit. The ATC provides a variable duty cycle ground to the 12.0v signal based on input from the Rear Booster Fan Rear Control switch.
NOTE: When the fan speed is set to low, the ATC provides a short duty cycle (less time grounding the signal voltage).
NOTE: As higher fan speeds are requested, the ATC increases the duty cycle (more time grounding the signal voltage).
NOTE: When the highest fan speed is requested, the duty cycle increases to where the signal pattern is almost a flat line (with brief voltage spikes).

Set the fan speed to low, then slowly raise the fan speed to high while observing the DRBIII® display.
The voltage on the scope pattern should cycle from approximately 0 volts (duty cycle on) to 12.0 volts (duty cycle off) for all fan speeds.
The duty cycle pattern should change smoothly as the fan speed changes from low to high.
Does the DRBIII® display the voltage range and duty cycle as described above?
  1. Yes: Replace the Rear Booster Fan Power Module in accordance with the Service Information.

    Perform BODY VERIFICATION TEST VER-1 .

  2. No: Replace the Automatic Temperature Control (ATC) in accordance with the Service Information.

    Perform BODY VERIFICATION TEST VER-1 .

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