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Q: Dimmer light not working - 1991 GMC K2500

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My dimmer light wasn't working in my 5 speed truck, and the instrument panel lights quit working along with the warning buzzer for turned on lights when you open the door. I am not positive about the buzzer being in this truck, but I’m sure about the panel lights going out. So I took off the dimmer switch to test the wiring. There were 4 wires and the only continual hot lead was the white wire. When I turned on the lights I only had the one white hot lead. When I turned the dimmer knob all the way up, my lower cab lights under the dashboard worked normally. My lights worked well - both the low and high beams. Should there be more than 1 hot lead on the dimmer switch when the lights are off? Should one of the other wires be a hot lead when the lights are on? Do you know what should be hot and what shouldn’t be hot on the wires to the dimmer switch? Are there relays I should be checking? It looks like there is a relay panel above the emergency brake foot pedal with 3 relay box devices.

A: Hey there, thanks for writing in about your...

Hey there, thanks for writing in about your 1991 GMC K2500. You should have power on the white wire, dark green wire, and also the brown wire when the dashboard lights dimmer is turned on. If you need help having this checked, a qualified professional from YourMechanic can come to your car’s location to inspect the light circuitry in order to have this corrected.

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