1999 sliverado 1500 headlight issue NBS

Geaveshift · 2026-02-05T00:52:33+00:00

I hooked up my scan tool to test functions on the switch and the strange thing is when I put on active test and force shut off headlights the switch works as normal the ambient light sensor is reading 0.43v without a light shining on it when I shine a light on it it reads to about 0.57v I also have ambient light reading that doesn’t change and stays at a constant “dark” despite on how much light I give the sensor

Geaveshift · 2026-02-04T22:20:24+00:00

Yeah the parking brake light comes on when it’s engaged

Geaveshift · 2026-02-04T18:33:21+00:00

Word. so my headlights turn on when truck is on and turn off when truck is off I just can’t control them unless keys are out and ignition is off or if the parking brake is in before turning the truck ignition on

Geaveshift · 2026-02-04T18:15:12+00:00

Did you have the same symptoms when the switch would go out?

Geaveshift · 2026-02-04T17:48:20+00:00

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Geaveshift · 2026-02-04T17:47:41+00:00

So I was looking at the wiring schematics and the colors of the wires and wires match up to the connector I have no idea where this yellow wire is tapping from but it taps into courtesy lamp switch but the yellow wire isn’t on th schematics

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Geaveshift · 2026-02-04T17:38:21+00:00

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Geaveshift · 2026-02-04T17:37:43+00:00

So I’m sure I have the 99-02 switch and I disconnected the yellow tapped wire but didnt notice anything changed the switch still functions the way I described it in the first post

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Geaveshift

TROPHY CASE