System Tests: Notes
- Turn ignition switch to ON position. Press rear defogger switch to ON position. If rear defogger grid begins to warm and rear defogger indicator illuminates, go to next step. If rear defogger indicator illuminates but rear defogger grid does not warm, go to step 3). If rear defogger grid warms but defogger indicator does not illuminate, check for open in Black wire between rear defogger switch and ground. If circuit is okay, replace rear defogger switch. If rear defogger indicator does not illuminate and rear defogger grid does not begin to warm, go to step 5).
- Press rear defogger switch to OFF position. If rear defogger indicator goes out and rear defogger grid begins to cool, rear defogger system is functioning normally. If rear defogger indicator does not go out and rear defogger grid does not begin to cool, go to step 6).
- Connect test light between rear defogger Red/White wire terminal and ground. If test light does not illuminate, go to next step. If test light illuminates, check for open in Black wire between rear defogger and ground connection located inside rear door, near license plate lights. If circuit is okay, repair or replace rear defogger grid.
- Using test light, backprobe between rear defogger switch Blue 6-pin connector terminal No. 2 (Red/White wire) and ground. If test light illuminates, repair open in Red/White wire between rear defogger switch and rear defogger. If test light does not illuminate, replace rear defogger switch.
- Using test light, backprobe between rear defogger switch connector terminal No. 1 (Yellow/Green wire) and ground. See Fig 1
. If test light does not illuminate, repair open in Yellow/Green wire between rear defogger switch and fuse block No. 2. If test light illuminates, replace rear defogger switch.
- Disconnect rear defogger switch connector. Connect test light between rear defogger switch connector terminal No. 2 (Red/White wire) and ground. If test light illuminates, repair short to voltage in Red/White wire between rear defogger switch and rear defogger. If test light does not illuminate, replace rear defogger switch.
Courtesy of GENERAL MOTORS CORP.