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

I1 CHECK THE REAR WINDOW DEFROST GRID VOLTAGE

Disconnect: Rear Window Defrost Relay

Disconnect: Rear Window Defrost Grid C402A.

Ignition ON.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C402A-1	Courtesy of FORD MOTOR COMPANY	Ground

Is any voltage present?

Yes	REFER to OEM Electrical Wiring Diagram Introduction to identify the possible causes of the circuit short.

GO to I2

I2 CHECK THE HVAC (HEATING, VENTILATION AND AIR CONDITIONING) MODULE OUTPUT

NOTE: 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.

Start the engine.

Connect:

Positive Lead	Measurement / Action	Negative Lead
Courtesy of FORD MOTOR COMPANY Rear Window Defrost Relay, socket pin 1	Courtesy of FORD MOTOR COMPANY	Courtesy of FORD MOTOR COMPANY Rear Window Defrost Relay, socket pin 2

Does the test light illuminate?

Yes

GO to I3

No	INSTALL a new rear window defrost relay.

I3 CHECK THE HVAC (HEATING, VENTILATION AND AIR CONDITIONING) MODULE OUTPUT

Ignition OFF.

Disconnect: HVAC Module C228A.

Ignition ON.

Connect:

Positive Lead	Measurement / Action	Negative Lead
Courtesy of FORD MOTOR COMPANY Rear Window Defrost Relay, socket pin 1	Courtesy of FORD MOTOR COMPANY	Courtesy of FORD MOTOR COMPANY Rear Window Defrost Relay, socket pin 2

Does the test light illuminate?

Yes	REPAIR the short to ground in the rear window defrost relay control circuit.

GO to I4

I4 CHECK FOR CORRECT HVAC (HEATING, VENTILATION AND AIR CONDITIONING) MODULE OPERATION

Ignition OFF.

Disconnect and inspect all the HVAC module 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 HVAC module 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 HVAC module. REFER to: Heating, Ventilation and Air Conditioning (HVAC) Control Module .

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.