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 MANUALSCHEVROLET1990SUBURBAN V2500, 6.2 J, 475/M40REPAIR AND DIAGNOSIS (SINGLE PAGE)ACCESSORIES & EQUIPMENTHEATED GLASS/DEFOGGERSDEFOGGER - REAR WINDOWTROUBLE SHOOTINGGRID TEST & REPAIR
1990 Chevrolet Suburban V2500, 6.2 J, 475/M40
Grid Test & Repair
1990 Chevrolet Suburban V2500, 6.2 J, 475/M40SECTION Grid Test & Repair
- Start engine and turn defogger system on. Ground test light and lightly probe each grid line. Move test light from feed wire side of grid to ground side. See Figure .
- Test light should gradually dim as it is moved across grid. Be sure to check each grid in at least 2 places to avoid the possibility of bridging a gap with test light.
- If test light shows full brilliance at both ends of grid, check for loose ground wire contact at cab body. If test light goes out as it is moved across grid, a break has been detected. Use a grease pencil to mark break(s) on outside of window.
- To repair grid, turn system off and disconnect negative battery cable. Clean area to be repaired with steel wool. Wipe area clean with denatured alcohol. Be sure to clean 1/4" (6 mm) beyond each side of break.
- With glass at room temperature of 70-90°F (20-32°C), position repair template over area to be repaired. Apply grid repair material to grid and remove template. Allow repair area to air dry for at least 24 hours.
- Test defogger operation to verify repair. If repair appears discolored, apply a coating of tincture of iodine. Allow iodine to dry for 30 seconds and carefully wipe off excess.
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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.