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.
Function Test
- Be careful not to scratch or damage the defogger wires with the tester probe.
- Before testing, check the No. 8 (30 A) fuse in the under-hood fuse/relay box and the No. 36 (10 A) fuse in the under-dash fuse/relay box.
- Check for voltage between the positive terminal (A) and body ground with the ignition switch and the defogger switch ON.
There should be battery voltage.
- If there is no voltage, check for:
- Faulty rear window defogger relay.
- Faulty climate control unit.
- An open in the RED wire to the positive terminal.
- If there is voltage, go to step 2.
- If there is no voltage, check for:
- Disconnect the negative terminal (B) from the rear window defogger.
- Check for continuity between the negative terminal (B) and body ground.
If there is no continuity, check for an open in the wire or poor ground (G801). If there is continuity, go to step 4.
- Reconnect the negative terminal to the rear window defogger.
- Turn the ignition switch ON (II) and the rear window defogger switch ON.
- Touch the voltmeter positive probe to each point on each defogger wire, and the negative probe to the negative terminal.
- If the voltage is as specified, the defogger wire up to that point is OK.
- If the voltage is not as specified, repair the defogger wire.
- If it is more than specified at one of the points, there is a break in the negative half of the wire.
- If it is less than specified at one of the points, there is a break in the positive half of the wire.
Use the Manual With the Right Hardware
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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.
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