NOTICE: The following step uses a test lamp to simulate normal circuit loads. Use only a Rotunda Test Lamp (SGT27000) or 250- 300mA incandescent bulb test lamp. To avoid connector terminal damage, use the Rotunda Flex Probe kit for the test lamp probe connection to the vehicle. Do not use the test lamp probe directly on any connector. Connect:
Positive Lead | Measurement / Action | Negative Lead |
|---|---|---|
Rear Window Defrost Relay, socket pin 1 | Rear Window Defrost Relay, socket pin 2 |
Does the test light illuminate?
Yes | GO to L3 |
|---|---|
No | INSTALL a new rear window defrost relay. |
L3 CHECK THE REAR WINDOW DEFROST RELAY CONTROL CIRCUIT FOR A SHORT TO GROUND
Ignition OFF. Disconnect: FCIM C2402A. Measure:
Click to display connectors
Positive Lead | Measurement / Action | Negative Lead |
|---|---|---|
Rear Window Defrost Relay, socket pin 2 | Ground |
Is the resistance greater than 10,000 ohms?
Yes | GO to L4 |
|---|---|
No | REPAIR the circuit. |
L4 CHECK FOR CORRECT FCIM (FRONT CONTROLS INTERFACE MODULE) OPERATION
Disconnect and inspect all the FCIM connectors. Repair:
corrosion (install new connector or terminals - clean module pins) damaged or bent pins - install new terminals/pins as necessary pushed-out pins - install new pins as necessary
Reconnect the FCIM connectors and all previously disconnected rear window defrost system connectors. Make sure they seat and latch correctly. Operate the system and determine if the concern is still present.
Is the concern still present?
Yes | CHECK OASIS for any applicable Technical Service Bulletins (TSBs). If a TSB exists for this concern, DISCONTINUE this test and FOLLOW TSB instructions. If no Technical Service Bulletins (TSBs) address this concern, INSTALL a new FCIM. Refer to the appropriate section in Group 415 for the procedure. |
|---|---|
No | The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues. |
Component Test- Grid Wire Test
1. Using a bright lamp in the vehicle, inspect the grid wire from the exterior. A broken grid wire will appear as a brown spot.
2. Run the engine at idle. Activate the rear window defrost switch. The indicator light should come on.
3. Working in the vehicle with a voltmeter, contact the broad red-brown stripes of the rear glass window (positive lead to B+ side and the negative lead to ground side). The meter should read 10-13 volts. A lower voltage reading indicates a loose ground connection.
2016 Mustang workshop publication supplied to Mustang Atlas. Original technical text and illustrations; HTML formatting by Mustang Atlas. Source page numbering is retained for traceability. Follow the configuration, revision, warnings, and cross-references in the material. About this edition.