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Home >> Ford >> 2012 >> Mustang Base, 2D Coupe, Automatic Trans >> Repair and Diagnosis >> External Pages >> Different car >> Section 291 (Windows And Glass - Glass, Frames And Mechanisms) >> Diagnosis And Testing >> Glass, Frames and Mechanisms >> Pinpoint Tests >> Pinpoint Test I: The Defrost System Does Not Shut Off Automatically >> Pinpoint Test I: The Defrost System Will Not Shut Off Automatically

Pinpoint Test I: The Defrost System Will Not Shut Off Automatically

WARNING: This page is about a different car, the 2013 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.
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. I1 CHECK REAR WINDOW DEFROST GRID POWER CIRCUIT FOR A SHORT TO VOLTAGE 
    • Disconnect: Rear Window Defrost Relay.
    • Disconnect: Rear Window Defrost Grid Power (Passenger Side Terminal).
    • Ignition ON.
    • Measure the voltage between rear window defrost grid power terminal, harness side and ground.
      Fig 1: Measuring Voltage Between Rear Window Defrost Grid Power Terminal And Ground
      G07934854Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes  : REPAIR circuit CRD06 (BN/YE) for a short to voltage. TEST the system for normal operation.
    • No  : If equipped with a power sliding rear window, GO to I2. If not equipped with a power sliding rear window, GO to  I4.
  2. I2 CHECK THE REAR WINDOW DEFROST SWITCH LED STATUS 
    • Observe the rear window defrost switch status.
    • Is the rear window defrost switch LED illuminated? 
    • Yes  : GO to I3.
    • No  : GO to  I4.
  3. I3 CHECK THE REAR WINDOW DEFROST FEEDBACK CIRCUIT FOR A SHORT TO VOLTAGE 
    • Ignition OFF.
    • Disconnect: Rear Window Defrost Grid Inline (passenger side) C3368.
    • Disconnect: HVAC Module - EATC C228B or HVAC Module - Electronic Manual Temperature Control (EMTC) C294A.
    • Ignition ON.
    • Measure the voltage between rear window defrost grid inline C3368-1, circuit CH122 (WH/OG), harness side and ground.
      Fig 2: Measuring Voltage Between Rear Window Defrost Grid Inline C3368-1, Circuit CH122 (WH/OG) And Ground
      G08344113Courtesy of FORD MOTOR CO.
    • Is any voltage present? 
    • Yes  : REPAIR the circuit. TEST the system for normal operation.
    • No  : GO to  I6.
  4. I4 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)  table . 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.
    • Connect the 12-volt incandescent test light between rear window defrost relay socket pin 2, circuit CRD02 (BN/BU) and rear window defrost relay socket pin 1, circuit CBB54 (VT/OG).
      Fig 3: Checking HVAC Module
      G06458883Courtesy of FORD MOTOR CO.
    • Does the test light illuminate? 
    • Yes  : GO to I5.
    • No  : INSTALL a new rear window defrost relay. TEST the system for normal operation.
  5. I5 CHECK THE REAR WINDOW DEFROST RELAY CONTROL CIRCUIT FOR A SHORT TO GROUND 
    • Ignition OFF.
    • Disconnect: HVAC Module - EATC C228B or HVAC Module - Electronic Manual Temperature Control (EMTC) C294A.
    • Measure the resistance between rear window defrost relay socket pin 2, circuit CRD02 (BN/BU), harness side and ground.
      Fig 4: Measuring Resistance Between Rear Window Defrost Relay Socket Pin 2, Circuit CRD02 (BN/BU) And Ground
      G06173673Courtesy of FORD MOTOR CO.
    • Is the resistance greater than 10, 000 ohms? 
    • Yes  : GO to I6.
    • No  : REPAIR short to ground in circuit CH122 (WH/OG). TEST the system for normal operation.
  6. I6 CHECK FOR CORRECT HVAC MODULE OPERATION 
    • Disconnect all HVAC module connectors.
    • Check for:
      • corrosion.
      • pushed-out pins.
    • Connect all HVAC module 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. REFER to HVAC - CLIMATE CONTROL SYSTEM (SERVICE INFORMATION) . 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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