Headlights not working?

1999 CHEVROLET SILVERADO

100,000 MILES • 5.3L • V8 • 4WD • AUTOMATIC

99CHEVY

MEMBER
2 POSTS

one day my headlights work, the next day they don't, i have replaced the bulbs, all lights work except dome light and headlights. i checked the fuses and the relays all checked out fine. i have taken off the cover of the steering column and checked the little blue wires to see if it's okay. I went as far as making some jumper wire to go directly from the battery to the headlight fuse slot and finally i would get them to come on. but that is bypassing everything in its electrical path to work properly. i do have DRLs. but i am not sure how to check wiring to find actual issue. i need to find the component in which the electrical travels through that is between the relay and the fuse. does it go through the multi-function before fuses or vice versa? help?

Mar 25, 2023 at 10:18 AM

STEVE W.

✓Experienced Mechanic
15,308 POSTS

Okay, from your description it sounds like the issue could be in the body control module itself. On that truck the relay goes to constant power, then it feeds the two fuses. From there it goes out to the headlamp bulbs and then through the dimmer switch to ground. You said that you made jumpers that went from the battery to the headlight fuses and that made the lights work? That would bypass the power relay and its control wiring that comes from the body module. It also shows that the dimmer switch and grounds are not the problem as those are after the lamps. So, it has to be on the switched relay side, it isn't being turned on. Attached is the wiring diagram. Being an intermittent it may take a bit to track down. I would start at the relay and see if the relay control voltage is on pin 85. If it is missing then look at the headlight switch itself.

Mar 26, 2023 at 8:24 AM

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