Skip the auto shop - Our mechanics make house calls

Q: Dimmer light not working - 1991 GMC K2500

asked by on

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.

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Dash lights going in and out

I will assume the lights are completely turning on and off randomly. In this case, there is a possible loose connection behind the instrument cluster. Other vehicles of the same model with similar symptoms were affected by a faulted dimmer...

Q: Battery drained and car won't start

I would recommend having your vehicle inspected by a technician who is qualified to service your hybrid vehicle electrical systems. If your vehicle's 12 volt battery has failed, they should be able to replace it very easily for you and...

Q: Car is starving for fuel at idle after warming up - 1991 Ford Mustang

Hi there. I usually start with the idle air valve in these cases, as it sounds like it might be sticking. Checking fuel supply - fuel pressure, filter, dirty injectors, as you have noted - is a good idea. You...

Related articles

Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.