Instrument Panel Dimmer Not Working

[gearheadE30]

I did some searching, but was unable to find any information on my problem. Just bought a '98 K1500 ECSB with the ubiquitous non-functional headlights, and dash lights that do not dim. I assumed that the rheostat had failed, so I bought a new headlight switch and multifunction switch and got those installed last night. The original multifunction switch had broken wires along the steering column, which took care of the headlights, but the new headlight switch/dash dimmer didn't fix the backlight issue.

The dash runs at full brightness regardless of dimmer position. The top position of the dimmer turns the interior lights on, as it should. As far as I can tell, all common ground locations under the dash are in good shape and are tight, and there are no more broken wires. The only electronic alteration on this truck is an aftermarket radio; everything else is original and unmolested.

Any ideas? Even the full brightness headlights suck, and it is even worse with the dash lights blinding me.

 

[gearheadE30]

Well, I figured it out. Whoever installed the radio had tied together the wires for headlight signal and dimmer, so it was backfeeding all of the dash lights around the dimmer rheostat via the signal wire.

After working with mostly vintage German vehicles, I'm pretty blown away by how the whole dash just snaps together. No wonder they creak so much. At least it's incredibly easy to work on.

 

[torq4u]

awe crap , just did a radio in mine and now I have that gremlin . just no dash lights and temp control blacks out when I turn on my lights . i'm glad yours works now .