Rear Window Defogger: Inspection

CAUTION: When wiping stain on glass off with cloth, use a dry and soft cloth and move it in the direction of heat wire extension to avoid damage to heat wire.

Turn the ignition switch to ON.
Turn the defogger switch to ON.
Wrap the tips of tester pins with aluminum foil to avoid damage to heat wire.

Fig 1: Wrapping Tips Of Tester Pins With Aluminum Foil
Courtesy of SUBARU OF AMERICA, INC.

Measure the voltage at wire center with DC voltmeter.

Standard voltage:

Approx. 6 V

Fig 2: Measuring Voltage At Wire Center With DC Voltmeter

Courtesy of SUBARU OF AMERICA, INC.

VOLTAGE CHART

Voltage	Criteria
Approx. 6 V	OK
Approx. 12 V or 0 V	Broken

NOTE:

If the measured value is 12 volts, heat wire is open between wire center and positive (+) end.
If zero volt, heat wire is open between wire center and ground.

Apply positive lead of voltmeter to positive terminal of heat wire, and then move the negative lead along the wire up to negative terminal end. If voltage changes from zero to several volts during movement of lead, heat wire is open at the voltage change points.