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Pinpoint Test H : The Defrost System Is Inoperative

  1. H1 CHECK THE REAR WINDOW DEFROST GRID VOLTAGE

    • Disconnect: Rear Window Defrost Grid C402A.

    • Start the engine.

    • Activate the rear defrost switch.

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      C402A-1
      GFD335985Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the voltage greater than 11 volts? 

    Yes  GO to  H2
    No  VERIFY BJB fuse 12 (40A) is OK. If not OK, REFER to OEM Electrical Wiring Diagram Introduction to identify the possible causes of the circuit short. If OK, GO to  H3

  2. H2 CHECK THE REAR WINDOW DEFROST GRID GROUND CIRCUIT FOR AN OPEN

    • Ignition OFF.

    • Disconnect: Window Defrost Grid C402B.

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      C402B-1
      GFD335986Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the resistance less than 3 ohms? 

    Yes  CARRY OUT the Grid Wire Test. Refer to Component Test- Grid Wire Test . REPAIR the rear window defrost grid or INSTALL a new rear window glass if necessary. REFER to: Heated Window Grid Wire Repair .
    No  REPAIR the circuit.

  3. H3 CHECK THE VOLTAGE SUPPLY TO THE REAR WINDOW DEFROST RELAY

    • Ignition OFF.

    • Disconnect: Rear Window Defrost Relay.

    • Ignition ON.

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      GFD335987Courtesy of FORD MOTOR COMPANY

      Rear Window Defrost Relay, socket pin 1
      GFD335985Courtesy of FORD MOTOR COMPANY
      		 Ground
      GFD335987Courtesy of FORD MOTOR COMPANY

      Rear Window Defrost Relay, socket pin 3
      GFD335985Courtesy of FORD MOTOR COMPANY
      		 Ground

    Are the voltages greater than 11 volts? 

    Yes  GO to  H4
    No  REPAIR the circuit or INSTALL a new BJB as necessary.

  4. H4 CHECK THE HVAC (HEATING, VENTILATION AND AIR CONDITIONING) MODULE OUTPUT

    NOTE: The following step uses a test lamp to simulate normal circuit loads. Use only a Rotunda Test Lamp (SGT27000) or 250- 300mA incandescent bulb test lamp. To avoid connector terminal damage, use the Rotunda Flex Probe kit for the test lamp probe connection to the vehicle. Do not use the test lamp probe directly on any connector.

    • Start the engine.

    • Connect:
      Positive Lead Measurement / Action Negative Lead
      GFD335987Courtesy of FORD MOTOR COMPANY

      Rear Window Defrost Relay, socket pin 1
      GFD335549Courtesy of FORD MOTOR COMPANY
      GFD335987Courtesy of FORD MOTOR COMPANY

      Rear Window Defrost Relay, socket pin 2

    • Activate the rear window defrost switch.

    Does the test light illuminate? 

    Yes  GO to  H5
    No  GO to  H6

  5. H5 CHECK THE REAR WINDOW DEFROST RELAY

    • Carry out the rear window defrost relay component test. Refer to Component Testing for schematic and connector information.

    Did the rear window defrost relay pass the component test? 

    Yes  REPAIR the open rear window defrost relay output circuit.
    No  INSTALL a new rear window defrost relay.

  6. H6 CHECK THE REAR DEFROST SWITCH (CC_SW_R_DEF) PID (PARAMETER IDENTIFICATION)

    • Ignition ON.

    • Using a diagnostic scan tool, view FCIMB PIDs (Parameter Identifications).

    • Monitor the CC_SW_R_DEF PID while pressing and releasing the rear window defrost switch.

    Does the PID agree with the rear window defrost switch status? 

    Yes  GO to  H7
    No  Refer to FCIM Guided Routine Testing .

  7. H7 CHECK THE REAR WINDOW DEFROST RELAY CONTROL CIRCUIT FOR A SHORT TO VOLTAGE

    • Ignition OFF.

    • Disconnect: HVAC Module C228A.

    • Ignition ON.

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      GFD335987Courtesy of FORD MOTOR COMPANY

      Rear Window Defrost Relay, socket pin 2
      GFD335985Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is any voltage present? 

    Yes  REPAIR the circuit.
    No  GO to  H8

  8. H8 CHECK THE REAR WINDOW DEFROST RELAY CONTROL CIRCUIT FOR AN OPEN

    • Ignition OFF.

    • Measure:
      Positive Lead Measurement / Action Negative Lead
      GFD335987Courtesy of FORD MOTOR COMPANY

      Rear Window Defrost Relay, socket pin 1
      GFD335986Courtesy of FORD MOTOR COMPANY
      		 C228A-25

    Is the resistance less than 3 ohms? 

    Yes  GO to  H9
    No  REPAIR the circuit.

  9. H9 CHECK FOR CORRECT HVAC (HEATING, VENTILATION AND AIR CONDITIONING) MODULE OPERATION

    • Ignition OFF.

    • Disconnect and inspect all the HVAC module connectors.

    • Repair:

      • corrosion (install new connector or terminals - clean module pins)
      • damaged or bent pins - install new terminals/pins as necessary
      • pushed-out pins - install new pins as necessary

    • Reconnect the HVAC module connectors and all previously disconnected rear window defrost system connectors. Make sure they seat and latch correctly.

    • Operate the system and determine if the concern is still present.

    Is the concern still present? 

    Yes  CHECK OASIS for any applicable Technical Service Bulletins (TSBs). If a TSB exists for this concern, DISCONTINUE this test and FOLLOW TSB instructions. If no Technical Service Bulletins (TSBs) address this concern, INSTALL a new HVAC module. REFER to: Heating, Ventilation and Air Conditioning (HVAC) Control Module .
    No  The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues.
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