System Testing
- Before proceeding with system test, check rear defogger fuse in fuse/relay box. Fuse/relay box is located near left kick panel. Ensure all connections are clean and secure. Ensure rear defogger grid is continuous and is NOT damaged. Repair as required. If rear defogger still does not work, go to step 2).
- Turn ignition and rear defogger switches on. If defogger indicator light comes on and rear window starts to warm, go to step 3). If rear defogger indicator light comes on but rear window does not warm, go to step 4). If rear window warms but defogger indicator light does not light, check for burned bulb. If bulb is okay, check Black ground wire between rear defogger switch and ground connection. Ground connection is located behind left kick panel. If defogger indicator light does not light and rear window does not warm, go to step 6).
- Turn rear defogger switch off. If rear defogger indicator light goes out and rear window cools, system is working properly. If rear defogger indicator light remains on and rear window does not cool, go to step 7).
- Ensure ignition and rear defogger switches are on. Connect a test light to rear defogger connector Black wire (passenger side). If test light glows, repair Black ground wire between rear defogger and ground connection. Ground connection is located on left side of tailgate, behind trim panel. See Fig 1
. If test light does not light, go to step 5).
- Using a test light, backprobe rear defogger switch connector terminal No. 1 (Red/White wire). If test light glows, repair open in Red/White wire and/or Black wire between rear defogger switch and rear defogger. If test light does not light, replace rear defogger switch.
- Using a test light, backprobe rear defogger switch connector terminal No. 2 (Yellow/Green wire). If test light does not light, go to step 4). If test light glows, repair open in Yellow/Green wire between fuse/relay box and rear defogger switch. Fuse/relay box is located near left kick panel.
- Disconnect rear defogger switch connector. Connect a test light to rear defogger switch connector terminal No. 1 (Red/White wire). If test light glows, repair short in Red/White wire and/or Black wire between rear defogger switch and rear defogger. If test light does not light, replace rear defogger switch.
Courtesy of GENERAL MOTORS CORP.