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Home >> Ford >> 2002 >> Crown Victoria Base, 4.6 9 >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Heated Glass/Defoggers >> Rear Window Defogger System >> Component Tests >> Grid Filament Test

Grid Filament Test

  1. Shine a strong light through grid from inside vehicle. Inspect grid from outside. Broken grid lines will appear as Brown spots. Run engine at idle. Turn rear window defogger switch to ON. Switch indicator light should illuminate.
  2. Connect negative lead of a voltmeter to ground. Touch positive lead to both wide Red/Brown strips on rear window. Meter should indicate 10-13 volts on one side and zero volts on the other side. If voltage is lower, window grid ground wire (pigtail) connection is loose, repair as necessary.
  3. With voltmeter negative lead grounded, touch voltmeter positive lead to each grid line at its midpoint. A reading of about 6 volts indicates grid line is good. A zero reading indicates grid line is broken between midpoint and power side of grid. A 12-volt reading indicates grid line is broken between midpoint and ground. Repair grid filament as necessary. See GRID FILAMENT REPAIR  under ON-VEHICLE SERVICE.
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