Rear Window Defogger Wire Inspection and Repair: Inspection

NOTE:

When cleaning rear window glass, use a dry cloth to wipe it along wire direction.
When cleaning glass, do not use detergent or abrasive-containing glass cleaner.
When measuring wire voltage, use a tester with negative probe (3) wrapped with a tin foil (2) which should be held down on wire (1) by finger pressure.

Fig 1: Identifying Tester With Negative Probe Wrapped With Tin Foil

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Checking wire damage.

Turn ignition switch ON.
Turn defogger switch ON.
Use a voltmeter (1) to check voltage at the center of each heat wire, as shown.
If measured voltage is 10 V, wire must be damaged between its center and positive end. If voltage is zero, wire must be damaged between its center and ground.

DAMAGE CHECK FOR DEFOGGER WIRE

Voltage	Criteria
(A): Approx. 5 V	Good (No break in wire)
(A), (B): Approx. 10 V or 0 V	Broken wire

Fig 2: Checking Voltage At Center Of Each Heat Wire

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Locating damage in wire.
1. Touch voltmeter positive (+) lead to heat wire positive terminal end.
2. Touch voltmeter negative (-) lead with a foil strip to heat wire positive terminal end, then move it along wire to the negative terminal end.
3. The place where voltmeter fluctuates from zero to several volts is where there is damage.

NOTE: If heat wire is free from damage, voltmeter should indicate 12 V at heat wire positive terminal end and its indication should decrease gradually toward zero at the other terminal (ground).

Fig 3: Locating Damaged Wire

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