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04-08-48-001D Rear Window Defogger - Broken Heating Grid Detection Method - (Apr 17 2012) Defoggers Rear Glass - part 2

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Start the engine and turn onthe back window defogger. A distinct color change will take place at each conductivegrid line. Repeat for the bottom grid lines until they have all been checked in thedriver side zone.Repeat the process for the passenger side and center area zones.If no color change is noted for a grid line, place a crayon or china marker checkmark beside it. Mark each grid line in the zone where it is non-conductive and, therefore,not heating up. More than one broken grid line may be found.Method using portable infrared thermometer:Start the engine and turn on the rear back window defogger.From inside the vehicle, start at the top driver side grid line and slowly run theportable infrared thermometer vertically down the rear window contacting each gridline. You should be able to see a district variation in temperature readings.Mark each grid line in the zone where it is non-conductive and, therefore, not heatingup. More than one broken grid line may be found.Repeat the process for the passenger side and center area zones.If a broken defogger grid is detected, the recommended repair is rear window replacement.

GM bulletins are intended for use by professional technicians,NOT a "do-it-yourselfer".  They are written to inform thesetechnicians of conditions that may occur on some vehicles, or toprovide information that could assist in the proper service of avehicle.  Properly trained technicians have the equipment,tools, safety instructions, and know-how to do a job properly andsafely.  If a condition is described, DO NOT assume that thebulletin applies to your vehicle, or that your vehicle will havethat condition.  See your GM dealer for information on whetheryour vehicle may benefit from the information.

#04-08-48-001D: Rear Window Defogger - Broken Heating Grid Detection Method - (Apr 17, 2012) Defoggers Rear Glass

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