What is wrong with the instrument panel lights on my 2003 GMC Envoy XL?

Answer 1

I have a 2003 GMC Envoy XL SLT. I was driving the other night and from out of nowhere my instrument panel lights started fading in and out. This did not affect the headlights, tail lights, or brake lights, warning lights, only thing affected was the brightness of the instrument panel lights. When they are not fading in and out, they are bright as normal. I notice however that when I turn on the headlights and fog lamps that's when the issue arises. I am thinking it is the instrument panel dimmer switch (see photo). Is there something else I should be looking for? Ive hear it could be the alternator but wouldn't that affect everything? I do realize that at night with the headlights on, that the instrument panel lights dim somewhat to make it easier on the eyes. but, the lights are going completely dark at times and then going back to normal brightness. Adjusting the instrument panel dimmer knob has no affect other than when I turn it all the way to turn on the interior lights, which works fine.

Answer 2

If they're fading in and out, I would say the dimmer switch is a definite possibility, and the other thing I'd be looking for is a loose ground. I would suspect a loose ground more so, as a faulty dimmer switch would be expected to cause the lights to remain consistently dim. At the end of the ground wire will usually be a ring terminal which goes around the ground post... exactly where it is, I couldn't tell you without looking at a wiring diagram of the vehicle and chasing the ground wire, as I don't know offhand (I know the GMT330 platform well, but 2003 was the year that TrailBlazer and Envoy became actual models, based on the GMT360/370 platform, rather than just trim packages for the Blazer and Jimmy, and I'm not so familiar with that platform). Anyhow, that ground point is most likely on the firewall somewhere, and the ground wire will have a ring terminal at the end, typically... I'd look for breakage and fraying at the point where the wire connects to the ring terminal, then move on to the dimmer switch from there.