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 MANUALSCHEVROLET1986S10 BLAZER 2.5 E, 4WD, STANDARD, ML2REPAIR AND DIAGNOSISACCESSORIES & EQUIPMENTHEATED GLASS/DEFOGGERSDEFOGGER - REAR WINDOWTESTINGCIRCUIT
1986 Chevrolet S10 Blazer 2.5 E, 4WD, Standard, ML2
Defogger - Rear Window: Testing: Circuit
1986 Chevrolet S10 Blazer 2.5 E, 4WD, Standard, ML2SECTION Circuit
- Turn ignition switch to "OFF" position. Carefully remove defogger timer/relay from behind instrument panel. Pull timer/relay down, leaving wiring harness connected. Attach negative wire of test lamp to ground.
- Probe positive side of test lamp to Orange/Black wire (from behind connector). Battery voltage should be present at this point. Probe positive side of test lamp to Purple/White wire. No voltage should be present.
- Probe positive side of test lamp to Black wire. No voltage should be present at this point. Turn ignition on. Probe positive side of test lamp to Pink/Black wire. Battery voltage should be present at this point.
- Probe positive side of test lamp to Black wire. No voltage should be present at this point. Depress defogger control switch, and hold in "OFF" position. Probe positive side of test lamp to Lt. Blue wire. No voltage should be present at this point.
- Depress defogger control switch, and hold in "ON" position. Probe positive side of test lamp to Lt. Blue wire. Eleven volts should be present at this point, and "ON" indicator should be lit.
- Release defogger control switch. Probe positive side of test lamp to Lt. Blue wire. 4-8 volts should be present at this point, and "ON" indicator should remain lit.
- Probe positive side of test lamp to Orange/Black wire. Eleven volts should be present at this point. Probe positive side of test lamp to Purple/White wire. Eleven volts should be present at this point.
- Probe positive side of test lamp to Black wire. No voltage should be present at this point. Probe positive side of test lamp to Lt. Blue wire. Between 8 and 12 volts should be present at this point.
- Probe positive side of test lamp to Black wire on passenger's side of rear window defogger. No voltage should be present at this point. Probe positive side of test lamp to Black wire on driver's side of rear window defogger. 10-11 volts should be present at this point.
- Probe positive side of test lamp to middle of defogger grid. 10-11 volts should be present at this point. Depress and release defogger control switch. "ON" indicator should go out. Install defogger timer/relay.
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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.