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.
Rear Window Defogger Operation
Battery positive voltage is supplied through the RR DEFOG fuse, in the underhood fuse block, to the RR DEFOG relay switch. With the ignition in the ON position, ignition 3 voltage is supplied through the HTR A/C IGN fuse, in the underhood fuse block, to the HVAC control assembly and the RR DEFOG relay coil. When you depress the rear window defogger switch, the HVAC control assembly illuminates the rear window defogger indicator and grounds the control circuit of the RR DEFOG relay. This energizes the RR DEFOG relay and allows battery positive voltage to the rear window defogger grid. Ground for the rear window defogger grid is provided by G402.
When you start the engine and press the rear window defogger switch for the first time, the defogger cycle lasts for 10 minutes. Further operation results in 5 minute defogger cycles. The defogger cycle resets to 10 minutes when you cycle the ignition to the OFF position and then back to the ON position.
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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.