Testing Precautions

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 1990 Mercury Sable, 1990 Mercury Grand Marquis, 1990 Lincoln Town Car, 1990 Lincoln Continental, and 1990 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.

WARNING: This system operates at 30-70 volts when activated. To prevent injury, use caution when testing electrical system.

The heated windshield system will automatically turn off when the temperature in the passenger compartment is greater than 50°F (10°C). To test heated windshield at temperatures greater than 50°F (10°C), connect Black test lead to ground. Black test lead is on left side of engine compartment. See Fig 1 .

Fig 1: Test Lead Location
Courtesy of FORD MOTOR CO.
DO NOT test heated windshield system if windshield is cracked. Replace windshield if damaged or cracked.
The sense resistor will shut the system off if there is an open or intermittent circuit in the windshield. Connecting the Black test lead to ground will override this feature.
Use caution when testing the circuit between the alternator and the windshield - this circuit can carry up to 70 volts.