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Pinpoint Test H: The Defrost System Is Inoperative

NOTE: Use the correct probe adapter(s) from the Flex Probe Kit when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
  1. H1 CHECK THE REAR WINDOW DEFROST GRID VOLTAGE 
    • Disconnect: Rear Window Defrost Grid Power C402A.
    • Start the engine.
    • Activate the rear window defrost switch and measure the voltage between rear window defrost grid power C402A-1, circuit CRD06 (BN/YE), harness side and ground.
      Fig 1: Measuring Voltage Between Rear Window Defrost Grid Power C402A-1, Circuit CRD06 (BN/YE), Harness Side And Ground
      G06070954Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes  : GO to H2.
    • No  : GO to  H3.
  2. H2 CHECK THE REAR WINDOW DEFROST GRID GROUND 
    • Ignition OFF.
    • Disconnect: Rear Window Defrost Grid Ground C402B.
    • Measure the resistance between rear window defrost grid ground C402B-1, circuit GD149 (BK/GY), harness side and ground.
      Fig 2: Measuring Resistance Between Rear Window Defrost Grid Ground C402B-1, Circuit GD149 (BK/GY), Harness Side And Ground
      G06070955Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms? 
    • Yes  : CARRY OUT the Grid Wire Test. REPAIR the rear window defrost grid or INSTALL a new rear window glass. REFER to WINDOW GRID WIRE REPAIR . TEST the system for normal operation.
    • No  : REPAIR the circuit. TEST the system for normal operation.
  3. H3 CHECK THE POWER TO THE RELAY 
    • Ignition OFF.
    • Disconnect: Rear Window Defrost Relay.
    • Ignition ON.
    • Measure the voltage between rear window defrost relay socket pin 85, circuit CBP43 (GY) and ground; and between rear window defrost relay socket pin 30, circuit SBB20 (GN/RD) and ground.
      Fig 3: Measuring Voltage Between Rear Window Defrost Relay Socket Pin 85, Circuit CBP43 (GY) And Ground
      G06070956Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts for both measurements? 
    • Yes  : GO to H4.
    • No  : VERIFY Battery Junction Box (BJB) fuse 20 (40A) and Smart Junction Box (SJB) fuse 43 (10A) are OK. If OK, REPAIR the circuit (s). TEST the system for normal operation.

    If not OK, REFER to the appropriate Systems Wiring Diagrams to identify the possible causes of the circuit short. REPAIR the circuit. TEST the system for normal operation.

  4. H4 CHECK THE HVAC MODULE 
    NOTE: The following step uses a test light to simulate normal circuit loads. Use only the test light recommended in the Special Tool(s)  . To avoid connector terminal damage, use the Flex Probe Kit for the test light probe connection to the vehicle. Do not use the test light probe directly on any connector.
    • Start the engine.
    • Activate the rear defrost switch.
    • Connect a 12-volt incandescent test light between rear window defrost relay socket pin 86, circuit CH122 (WH/OG) and rear window defrost relay socket pin 85, circuit CBP43 (GY).
      Fig 4: Connecting 12-Volt Incandescent Test Light Between Rear Window Defrost Relay Socket Pin 86, Circuit CH122 (WH/OG) And Socket Pin 85, Circuit CBP43 (GY)
      G06070957Courtesy of FORD MOTOR CO.
    • 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 SYSTEM WIRING DIAGRAMS for component testing.

    • Did the rear window defrost relay pass the component test? 
    • Yes  : REPAIR open in circuit CRD06 (BN/YE). TEST the system for normal operation.
    • No  : INSTALL a new rear window defrost relay. TEST the system for normal operation.
  6. H6 CHECK THE REAR WINDOW DEFROST SWITCH (CC_SW_R_DEF) PID 
    • Ignition ON.
    • Enter the following diagnostic mode on the scan tool: Data Logger - FCIM  .
    • Monitor the FCIM 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  : INSTALL a new FCIM  . TEST the system for normal operation.
  7. H7 CHECK CIRCUIT CH122 (WH/OG) FOR AN OPEN 
    • Ignition OFF.
    • Disconnect: HVAC Module C228A.
    • Measure the resistance between rear window defrost relay socket pin 86, circuit CH122 (WH/OG) and HVAC module C228A-12  , circuit CH122 (WH/OG), harness side.
      Fig 5: Measuring Resistance Between Rear Window Defrost Relay Socket Pin 86 And HVAC Module C228A-12, Circuit CH122 (WH/OG), Harness Side
      G06070958Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms? 
    • Yes  : GO to H8.
    • No  : REPAIR the circuit. TEST the system for normal operation.
  8. H8 CHECK FOR CORRECT HVAC MODULE OPERATION 
    • Disconnect all HVAC module electrical connectors.
    • Check for:
      • corrosion.
      • pushed-out pins.
    • Connect all HVAC module electrical connectors and make sure they seat correctly.
    • Operate the system and verify the concern is still present.
    • Is the concern still present? 
    • Yes  : INSTALL a new HVAC module. TEST the system for normal operation.
    • No  : The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector. TEST the system for normal operation.
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