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

WARNING: This page is about a different car, the 2006 Mercury Grand Marquis and 2006 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: Use the correct probe adaptor(s) when making measurements. Failure to use the correct probe adaptor(s) may damage the connector.

G1 CHECK THE REAR WINDOW DEFROST SWITCH CIRCUIT FOR A SHORT TO GROUND
- Key in OFF position.
- Disconnect: DDM C501c.
- Measure the resistance between the DDM C501c-23, circuit 1010 (DB/OG), harness side and ground.
  
  Fig 1: Measuring Resistance Between DDM C501C-23, Circuit 1010 (DB/OG), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance greater than 10,000 ohms?
Yes : GO to G3.

No : GO to G2.
G2 CHECK HEATED CIRCUIT 1010 (DB/OG) FOR A SHORT TO GROUND
- Disconnect: Rear Window Defrost Switch C241.
- Measure the resistance between the DDM C501c-23, circuit 1010 (DB/OG), harness side and ground.
  
  Fig 2: Measuring Resistance Between DDM C501C-23, Circuit 1010 (DB/OG), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance greater than 10,000 ohms?
Yes : INSTALL a new rear window defrost switch. TEST the system for normal operation.

No : REPAIR the circuit. TEST the system for normal operation.
G3 CHECK CIRCUIT 688 (GY/LB) FOR A SHORT TO GROUND
- Disconnect: Rear Window Defrost Relay.
- Measure the resistance between the rear window defrost relay pin 86, circuit 688 (GY/LB), harness side and ground.
  
  Fig 3: Measuring Resistance Between Rear Window Defrost Relay Pin 86, Circuit 688 (GY/LB), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance greater than 10,000 ohms?
Yes : GO to G5.

No : GO to G4.
G4 CHECK THE DDM FOR A SHORT TO GROUND
- Disconnect: DDM C501b.
- Measure the resistance between the rear window defrost relay pin 86, circuit 688 (GY/LB), harness side and ground.
  
  Fig 4: Measuring Resistance Between Rear Window Defrost Relay Pin 86, Circuit 688 (GY/LB), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance greater than 10,000 ohms?
Yes : GO to G7.

No : REPAIR the circuit. TEST the system for normal operation.
G5 CHECK CIRCUIT 186 (BN/LB) FOR A SHORT TO VOLTAGE
- Key in ON position.
- Measure the voltage between the rear window defrost relay pin 30, circuit 186 (BN/LB), harness side and ground.
  
  Fig 5: Measuring Voltage Between Rear Window Defrost Relay Pin 30, Circuit 186 (BN/LB), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is voltage present?
Yes : REPAIR the circuit. TEST the system for normal operation.

No : GO to G6.
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 for schematic and connector information.
- Is the rear window defrost relay OK?
Yes : GO to G7.

No : INSTALL a new rear window defrost relay. TEST the system for normal operation.
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?
Yes : INSTALL a new DDM. REFER to MULTIFUNCTION ELECTRONIC MODULES . TEST the system for normal operation.

No : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.