Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSPONTIAC1991GRAND PRIX STE, 3.4 X, STANDARDREPAIR AND DIAGNOSISACCESSORIES & EQUIPMENTHEATED GLASS/DEFOGGERSDEFOGGER - REAR WINDOWTESTINGDEFOGGER GRID TEST
1991 Pontiac Grand Prix STE, 3.4 X, Standard
Defogger Grid Test
1991 Pontiac Grand Prix STE, 3.4 X, StandardSECTION Defogger Grid Test
- Start engine, and turn rear defogger control switch to ON position. Using a test light connected to ground, lightly touch each grid line. If test light shows full brilliance at both ends of all grid lines, check for loose ground wire. Test light brilliance should gradually change as test light probe is moved from left to right side of grid.
- Contact each grid line a few inches on either side of glass center line to eliminate possibility of missing a break in grid line. If a problem on a grid line is detected, place test light probe on grid line at left bus bar and move probe toward right bus bar until light goes out, indicating a break in grid line continuity. Refer to Fig 1 .
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.