Pinpoint Test O: The Defrost System Will Not Shut Off Automatically
Glass, Frames and Mechanisms
Pinpoint Test O: The Defrost System Will Not Shut Off Automatically - Fusion, Milan
Refer to Wiring Diagram Set 56 (Fusion/Milan/MKZ, Fusion Hybrid, Milan Hybrid, MKZ Hybrid), Heated Window for schematic and connector information. Diagrams By Number
Normal Operation
When the engine is running and the defrost switch (integral to the HVAC module or Front Controls Interface Module (FCIM), if equipped with navigation system) is pressed, the HVAC module activates the rear window defrost relay by grounding the relay coil. For vehicles equipped with navigation system, the FCIM sends the defrost request message to the HVAC module over the Controller Area Network (CAN). When the defrost relay is activated, voltage is supplied from the relay to the rear window defrost grid.
- DTC B1C83:14 (Rear Defog Relay: Circuit Short to Ground or Open) - sets when the HVAC module detects an open or short to ground on the rear window defrost relay control circuit.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Rear window defrost relay
- HVAC module
PINPOINT TEST O: THE DEFROST SYSTEM WILL NOT SHUT OFF AUTOMATICALLY - FUSION, MILAN
NOTICE: 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.
-------------------------------------------------
O1 CHECK THE REAR WINDOW DEFROST GRID POWER CIRCUIT 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.
- Is any voltage present?
Yes
REPAIR circuit CRD06 (BN/YE) for a short to voltage. TEST the system for normal operation.
No
GO to O2.
-------------------------------------------------
O2 CHECK THE REAR WINDOW DEFROST RELAY
- Start the engine.
- NOTICE: The following step uses a test light to simulate normal circuit loads. Use only the test light recommended in the Special Tools table at the beginning 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.
- Does the test light illuminate?
Yes
GO to O3.
No
INSTALL a new rear window defrost relay. TEST the system for normal operation.
-------------------------------------------------
O3 CHECK THE REAR WINDOW DEFROST RELAY CONTROL CIRCUIT 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.
- Is the resistance greater than 10,000 ohms?
Yes
GO to O4.
No
REPAIR short to ground in circuit CH122 (WH/OG). TEST the system for normal operation.
-------------------------------------------------
O4 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.
-------------------------------------------------