Headlights don't have a fuse. they have a breaker, so they will not fail on you entirely. When the breaker cools, they will come back on and the breaker on most cars is under the hood
I didn't find anything specifically for the 2006 GMC but every GMC truck fuse box I see has fuses for the headlights. Usually four fuses - low and high for both sides. --- I think it would be a low probability that all fuses are blown. The truck may have a body control module (BCM) that controls the headlights.
OK, that's fine, but they are breakers: from wiki: All Vehicle headlights are protected with circuit breakers instead of fuses because, when light bulbs fail, there is an ionizing arc internally that causes high current. You see that at home - when a light bulb fails you see an instant of very bright light. This pulse of high current can blow a fuse. It also can trip a circuit breaker, but the circuit breaker is designed to reclose while, once a fuse is blown, it stays blown. Headlights are a critical safety device. It is better to attempt automatic reclosure following a fault, than it is to leave the headlights off, in case the fault was temporary.
OK, I really did a lot more looking and it seems we are both right: From: ChevyTruckPages.net: Circuit breakers Headlamp and parking lamp circuit In addition to a fuse, the Headlamp circuits are protected by the Circuit Breaker in the light switch. An electrical overload on the breaker will cause the lights to go on and off, or in some cases to remain off.
Also..geez TS it gets better...Chevy seems to have this also: The following wiring harnesses are protected by a "fusible link" which is a special wire incorporated in the circuits: Headlamp high beam indicator Horn Air conditioning high blower Ignition circuits Starter Solenoid (pull in and hold) circuit Should an electrical overload occur, this wire will fail (burn) and prevent major damage to the harness.
GM does some strange things. My '02 Pontiac has fuses and the BCM controls the headlights. The center leg is always hot (12 Volts) and the ground side varies from 12 volts when off to 6 volts for DRL's to zero volts for headlights on. -- It's a real head scratcher if you don't know about it because with the lights off, all three wires show 12 volts to ground.
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