Pinpoint Test G: The Defrost System Does Not Shut Off Automatically

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

Normal Operation 

The key must be in the START or RUN position for the heated rear window to operate. When the rear window defrost switch is pressed, a momentary ground is supplied to the driver's door module (DDM) through circuit 1010 (DB/OG). The DDM provides a ground for the rear window defrost relay coil on circuit 688 (GY/LB). When the rear window defrost relay coil is energized, the relay switch closes, providing voltage to the heated rear window grid, the heated rear window indicator, and the heated exterior mirror (if equipped) through circuit 186 (BN/LB). The heated rear window grid and the rear window defrost switch are grounded through circuit 57 (BK).

This pinpoint test is intended to diagnose the following:

• Wiring, terminals or connectors
• Rear window defrost switch
• Rear window defrost relay
• DDM

PINPOINT TEST G: THE DEFROST SYSTEM DOES NOT SHUT OFF AUTOMATICALLY 

1. G1 CHECK THE REAR WINDOW DEFROST SWITCH CIRCUIT FOR A SHORT TO GROUND 
   • Key in OFF position.
   • Disconnect: DDM C501a
   Fig 1: Checking Circuit For Open or Short To Ground
   Courtesy of FORD MOTOR CO.
   • Measure the resistance between DDM C501a-23, circuit 1010 (DB/OG), harness side and ground.
   • Is the resistance greater than 10,000 ohms? 
   1. YES  : Go to  G3.
   2. NO  : Go to  G2.
2. G2 CHECK HEATED CIRCUIT 1010 (DB/OG) FOR A SHORT TO GROUND 
   • Disconnect: Rear Window Defrost Switch C241
   Fig 2: Checking Circuit For Open or Short To Ground
   Courtesy of FORD MOTOR CO.
   • Measure the resistance between DDM C501a-23, circuit 1010 (DB/OG), harness side and ground.
   • Is the resistance greater than 10,000 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.
3. G3 CHECK CIRCUIT 688 (GY/LB) FOR A SHORT TO GROUND 
   • Disconnect: Rear Window Defrost Relay
   Fig 3: Checking Circuit Resistance
   Courtesy 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 greater than 10,000 ohms? 
   1. YES  : Go to  G5.
   2. NO  : Go to  G4.
4. G4 CHECK THE DDM FOR A SHORT TO GROUND  
   • Disconnect: DDM C501b
   Fig 4: Checking Circuit Resistance
   Courtesy 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 greater than 10,000 ohms? 
   1. YES  : Go to  G7.
   2. NO  : REPAIR the circuit. TEST the system for normal operation.
5. G5 CHECK CIRCUIT 186 (BN/LB) FOR A SHORT TO VOLTAGE 
   • Key in ON position.
   Fig 5: Checking Circuit For Short To Voltage
   Courtesy of FORD MOTOR CO.
   • Measure the voltage between rear window defrost relay pin 87, circuit 186 (BN/LB), harness side and ground.
   • Is voltage present? 
   1. YES  : REPAIR the circuit. TEST the system for normal operation.
   2. NO  : Go to  G6.
6. G6 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  G7.
   2. NO  : INSTALL a new rear window defrost relay. TEST the system for normal operation.
7. G7 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.