2009 GMC Envoy Owner's Manual - Page 414

Electrical System Add-On Electrical Equipment Notice: Do not add anything electrical to the vehicle unless you check with your dealer/retailer first. Some electrical equipment can damage the vehicle and the damage would not be covered by the vehicle's warranty. Some add-on electrical equipment can keep other components from working as they should. Add-on equipment can drain the vehicle battery, even if the vehicle is not operating. The vehicle has an airbag system. Before attempting to add anything electrical to the vehicle, see Servicing Your Airbag-Equipped Vehicle on page 1-68. Headlamps The headlamp wiring is protected by four fuses. An electrical overload will cause a lamp to go on and off. If this happens, have the headlamp wiring checked right away. Windshield Wiper Fuses The windshield wiper motor is protected by a circuit breaker and a fuse. If the motor overheats due to heavy snow, etc., the wiper will stop until the motor cools. If the overload is caused by some electrical problem, have it fixed. Power Windows and Other Power Options Circuit breakers in the fuse block protect the power windows and other power accessories. When the current load is too heavy, the circuit breaker opens and closes, protecting the circuit until the problem is fixed or goes away. 5-112