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.

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.

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・Save up to 30%

Get a quote

What others are asking

Q: Brake light illuminated on the dash

Hello. The brake fluid level switch is probably getting stuck in the master cylinder causing the light to stay on. There could also be a leak in the brake system which would cause the light to stay on. What is...

Q: Sometimes when I get in the truck and start it I have no radio/windows and then a minute or two later it comes on????

Hi there, thanks for writing in about your 2002 Ford Excursion. It sounds like you have an intermittent electrical connection that is only causing problems during certain times. It may be the ignition switch, a bad ground, loose connector, corrosion,...

Q: No fuel to pumps - 1991 Mercedes-Benz 420SEL

Since you know how to use the multimeter, you are 2 steps ahead already! Start with power to the fuses (fuel pump), then the fuel pump relay to follow the power path. It's also possible that the ignition switch, and...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
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...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.