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Home >> Mercury >> 1996 >> Tracer LTS, Standard >> Repair and Diagnosis >> Accessories & Equipment >> Heated Glass/Defoggers >> Rear Window Defogger System >> System Testing >> Rear Window Does Not Defog

Rear Window Does Not Defog

  1. Check 20-amp DEFOG fuse in instrument panel fuse panel. If fuse is okay, go to step 3). If fuse is blown, replace fuse and go to next step.
  2. With defogger switch off, turn ignition on. If fuse blows again, repair Black/White wire for short to ground. If fuse does not blow, turn rear defogger switch on and check fuse. If fuse is okay, go to next step. If fuse blows, check Black/Dark Blue wire between rear defogger switch and rear window grid for short to ground.
  3. Remove rear defogger switch from instrument panel (leave wiring connected). Turn ignition switch on. Using a grounded test light, backprobe Black/White wire at switch connector. If test light glows, go to next step. If test light does not glow, repair Black/White wire between fuse panel and rear defogger switch.
  4. Using a grounded test light, backprobe Black/Dark Blue wire at switch connector. Turn defogger switch on. If test light glows, go to next step. If test light does not glow, replace rear defogger switch.
  5. Disconnect Black wire from rear defogger grid. Using a DVOM, measure resistance between rear window grid connector (Black wire) and ground. If resistance is greater than 5 ohms, repair Black wire between window grid and chassis ground point. If resistance is less than 5 ohms, check connections at rear defogger grid, and repair Black/Dark Blue wire between defogger switch and window grid.
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