Nissan 240sx S13 Rear Window Defogger: testing, on vehicle service and etc

Nissan 240sx S13



240SX uses a rear defogger relay, switch and rear window heater grid. 240SX uses a time control unit to limit heater grid "on" time.

REAR DEFOGGER RELAY

Relay supplies battery voltage to grid filament. See REAR DEFOGGER RELAY LOCATION table.

REAR DEFOGGER RELAY LOCATION

240SX Under Left End Of Dash, To Right Of Junction Block

TIME CONTROL UNIT

Unless control switch is turned off first, time control unit will turn off defogger after about 15 minutes. Time control unit, which also controls wiper delay, warning chimes, etc., is located behind left kick panel.

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TESTING

SYSTEM TESTING

1. Start engine. Turn rear defogger control switch on. Glass should feel warm after a few minutes. If glass is not warm, use a test light or voltmeter to check for battery voltage at grid feed wire. If battery voltage is present, perform GRID FILAMENT TEST .
2. If battery voltage is not present, check fuse, wiring harness and control switch. If these components are okay, check rear defogger relay. Check time control unit.

GRID FILAMENT TEST

1. To locate breaks in grid wire filaments, ensure battery voltage is present on feed side of grid. Connect voltmeter between middle portion of grid and vertical section of grid (at either end of window).
2. Probe entire length of grid. If voltmeter needle moves abruptly, check for break in grid at that point.

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ON-VEHICLE SERVICE

GRID FILAMENT REPAIR

1. Clean broken grid and its surrounding area with a cloth dampened in alcohol. Apply masking tape to both sides of grid line. See Fig. 1 .
2. Apply a small amount of silver conductive paint to tip of a drawing pen. Apply silver conductive paint on grid, overlapping existing grid approximately .20" (5 mm).
3. After 10 minutes, check repaired grid for continuity. DO NOT touch repaired area while test is being performed. If repaired area is okay, use a heat gun and apply hot air to repaired area for approximately 20 minutes. If a heat gun is not available, allow repaired area to dry for 24 hours.

Fig. 1: Repairing Rear Defogger Grid Element



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Nissan 240sx S13

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