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Home >> Ford >> 2009 >> Taurus X SEL, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1384 (Windows & Glass - Glass, Frames & Mechanisms) >> Diagnostic Tests >> Glass, Frames & Mechanisms >> Pinpoint Tests >> Pinpoint Test E: The Defrost System is Inoperative

Pinpoint Test E: The Defrost System is Inoperative

WARNING: This page is about a different car, the 2009 Mercury Grand Marquis and 2009 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.

Refer to appropriate SYSTEM WIRING DIAGRAMS article, Heated Windows for schematic and connector information.

Normal Operation 

The heated rear window is controlled by the driver's door module (DDM). The ignition switch must be in RUN for the DDM to operate. When the rear window defrost switch is pressed, the DDM provides a ground for the rear window defrost relay coil through circuit 688 (GY/LB). The rear window defrost relay coil is energized, providing battery voltage to the antenna module on circuit 186 (BN/LB). The antenna module then supplies voltage and ground to the heated rear window grid.

This pinpoint test is intended to diagnose the following:

PINPOINT TEST E: THE DEFROST SYSTEM IS INOPERATIVE 

CAUTION: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
  1. E1 CHECK THE REAR WINDOW DEFROST SWITCH CIRCUIT FOR AN OPEN 
    • Key in OFF position.
    • Disconnect: DDM C501a
      • Fig 1: Checking Circuit For Open or Short To Ground
      GF0013157Courtesy of FORD MOTOR CO.
    • While pressing the rear window defrost switch, measure resistance between DDM C501a-23, circuit 1010 (DB/OG), harness side and ground.
    • Is the resistance less than 5 ohms with the rear window defrost switch pressed? 
    1. YES  : CONNECT the DDM C501a. Go to  E4 .
    2. NO  : Go to  E2.
  2. E2 CHECK CIRCUIT 1010 (DB/OG) FOR AN OPEN 
    • Disconnect: Rear Window Defrost Switch C241
      • Fig 2: Checking Circuit For Open
      GF0013158Courtesy of FORD MOTOR CO.
    • Measure the resistance between DDM C501a-23, circuit 1010 (DB/OG), harness side, and rear window defrost switch C241-1, circuit 1010 (DB/OG), harness side.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  E3.
    2. NO  : REPAIR the circuit. TEST the system for normal operation.
  3. E3 CHECK CIRCUIT 57 (BK) FOR AN OPEN 
      Fig 3: Checking Circuit For Open
      GF0013159Courtesy of FORD MOTOR CO.
    • Measure the resistance between rear window defrost switch C241-2, circuit 57 (BK), harness side and ground.
    • Is the resistance less than 5 ohms? 
    1. YES  : INSTALL a new rear window defrost switch. TEST the system for normal operation.
    2. NO  : REPAIR the circuit. TEST the system for normal operation.
  4. E4 CHECK THE SIGNAL INPUT 
    • Disconnect: Rear Window Defrost Relay
    • Key in ON position.
    • Press the rear window defrost switch to ON.
      • Fig 4: Checking Circuit Resistance
      GF0013160Courtesy of FORD MOTOR CO.
    • Measure the resistance between rear window defrost relay pin 85, circuit 688 (GY/LB), harness side and ground.
    • Is the resistance less than 50 ohms? 
    1. YES  : Go to  E6.
    2. NO  : Go to  E5.
  5. E5 CHECK CIRCUIT 688 (GY/LB) FOR AN OPEN 
    • Key in OFF position.
    • Disconnect: DDM 501b
      • Fig 5: Checking Circuit For Open
      GF0013161Courtesy of FORD MOTOR CO.
    • Measure the resistance between rear window defrost relay pin 85, circuit 688 (GY/LB), harness side and the DDM C501b-15, circuit 688 (GY/LB), harness side.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  E12.
    2. NO  : REPAIR the circuit. TEST the system for normal operation.
  6. E6 CHECK CIRCUIT 185 (BK) FOR VOLTAGE 
      Fig 6: Checking Circuit for Voltage
      GF0013162Courtesy of FORD MOTOR CO.
    • Measure the voltage between rear window defrost relay pin 30, circuit 185 (BK), harness side and ground; and between rear window defrost relay pin 86, circuit 185 (BK), harness side and ground.
    • Is the voltage greater than 10 volts? 
    1. YES  : Go to  E7.
    2. NO  : VERIFY the battery junction box (BJB) fuse 107 (40A) is OK. If OK, REPAIR the circuit. TEST the system for normal operation.
  7. E7 CHECK THE REAR WINDOW DEFROST RELAY FOR CORRECT OPERATION 
    • Carry out the ISO relay test for the rear window defrost relay. Refer to COMPONENT TESTING article.
    • Is the rear window defrost relay OK? 
    1. YES  : Go to  E8.
    2. NO  : INSTALL a new rear window defrost relay. TEST the system for normal operation.
  8. E8 CHECK THE RELAY OUTPUT TO THE HEATED REAR WINDOW GRID 
    • Key in OFF position.
    • Connect: Rear Window Defrost Relay
    • Disconnect: Heated Rear Window Grid Connector
    • Key in ON position.
    • Press the rear window defrost switch to on.
      • Fig 7: Checking Circuit For Voltage
      GF0013163Courtesy of FORD MOTOR CO.
    • Measure the voltage between heated rear window grid connector harness side and ground.
    • Is the voltage greater than 10 volts? 
    1. YES  : Go to  E11.
    2. NO  : Go to  E9.
  9. E9 CHECK THE RELAY OUTPUT TO THE ANTENNA MODULE 
    • Key in OFF position.
    • Disconnect: Antenna Module
    • Key in ON position.
    • Press the rear window defrost switch to on.
      • Fig 8: Checking Circuit For Voltage
      GF0013164Courtesy of FORD MOTOR CO.
    • Measure the voltage between antenna module pin 1, circuit 186 (BN/LB), harness side and ground.
    • Is the voltage greater than 10 volts? 
    1. YES  : INSTALL a new antenna module. REFER to INFORMATION & ENTERTAINMENT SYSTEMS article. TEST the system for normal operation.
    2. NO  : Go to  E10.
  10. E10 CHECK CIRCUIT 186 (BN/LB) FOR AN OPEN OR SHORT TO GROUND 
    • Key in OFF position.
    • Disconnect: BJB Fuse 24 (10A)
    • Disconnect: Rear Window Defrost Relay
      • Fig 9: Checking Circuit For Open Or Short To Ground
      GF0013165Courtesy of FORD MOTOR CO.
    • Measure the resistance between antenna module pin 1, circuit 186 (BN/LB), harness side and pin 87, circuit 186 (BN/LB), harness side; and between antenna module pin 1, circuit 186 (BN/LB), harness side and ground.
    • Is the resistance less than 5 ohms between the antenna module and the rear window defrost relay, and greater than 10,000 ohms between the antenna module and ground? 
    1. YES  : INSTALL a new rear window defrost relay. TEST the system for normal operation.
    2. NO  : REPAIR the circuit. TEST the system for normal operation.
  11. E11 CHECK THE GROUND FOR THE HEATED REAR WINDOW GRID 
    • Key in OFF position.
    • Disconnect: Heated Rear Window Grid Ground Connector
      • Fig 10: Checking Circuit For Ground
      GF0013166Courtesy of FORD MOTOR CO.
    • Measure the resistance between heated rear window grid ground connector, circuit 57 (BK), harness side and ground.
    • Is the resistance less than 5 ohms? 
    1. YES  : CARRY OUT the heated rear window grid wire test. REFER to the Component Tests . REPAIR as necessary. TEST the system for normal operation.
    2. NO  : INSTALL a new antenna module. REFER to INFORMATION & ENTERTAINMENT SYSTEMS article. TEST the system for normal operation.
  12. E12 CHECK FOR CORRECT DDM OPERATION 
    • Disconnect all the DDM connectors.
    • Check for:
      • corrosion.
      • pushed-out pins.
    • Connect all the DDM connectors and make sure they seat correctly.
    • Operate the system and verify the concern is still present.
    • Is the concern still present? 
    1. YES  : INSTALL a new DDM. REFER to MULTIFUNCTION ELECTRONIC MODULES article. TEST the system for normal operation.
    2. NO  : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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