Pinpoint Test N: The Defrost System Will Not Shut Off Automatically - Fusion, MILAN

WARNING: This page is about a different car, the 2010 Mercury Milan, 2010 Lincoln MKZ, and 2010 Ford Fusion. 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.

N1 CHECK CIRCUIT CRD06 (BN/YE) FOR A SHORT TO VOLTAGE
- Disconnect: Rear Window Defrost Relay.
- Disconnect: Rear Window Defrost Grid Power C402A.
- Ignition ON.
- 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 & Ground
  Courtesy of FORD MOTOR CO.
- Is any voltage present?
- Yes: REPAIR circuit CRD06 (BN/YE) for a short to voltage. TEST the system for normal operation.
- No: GO to N2.
N2 CHECK THE REAR WINDOW DEFROST RELAY
- Start the engine.
  NOTE: The following step uses a test light to simulate normal circuit loads. Use only the test light recommended in SPECIAL TOOLS TABLE or equivalent. 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.
- Connect a 12-volt incandescent test light between rear window defrost relay socket pin 85, circuit CH122 (WH/OG) and rear window defrost relay socket pin 86.
  
  Fig 2: Connecting 12-Volt Incandescent Test Light Between Rear Window Defrost Relay Socket Pin 85, Circuit CH122 (WH/OG) & Rear Window Defrost Relay Socket Pin 86
  Courtesy of FORD MOTOR CO.
- Does the test light illuminate?
- Yes: GO to N3.
- No: INSTALL a new rear window defrost relay. TEST the system for normal operation.
N3 CHECK CIRCUIT CH122 (WH/OG) FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: HVAC Module - Electronic Manual Temperature Control (EMTC) C2357A or HVAC Module - Dual Automatic Temperature Control (DATC) C2356A.
- Start the engine.
- Measure the resistance between rear window defrost relay socket pin 85, circuit CH122 (WH/OG), harness side and ground.
  
  Fig 3: Measuring Resistance Between Rear Window Defrost Relay Socket Pin 85, Circuit CH122 (WH/OG), Harness Side & Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance greater than 10,000 ohms?
- Yes: GO to N4.
- No: REPAIR short to ground in circuit CH122 (WH/OG). TEST the system for normal operation.
N4 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. 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.