I put an aftermarket radio in the Blazer today. Took a while because the people that had it before me cut out the plug when they put their tape deck in. After getting the radio working, I put everything back together, and went to go for a ride. Now my dash lights won't come on, but if I put the parking lights on, the dome and floor lights come on as well. I've tried turning the dimmer switch plenty of times. I did notice that there were 2 extra wires that I couldn't figure out where they went, so I didn't do anything with them.

Is it possible that the interior lights are somehow tied into the radio harness?

 

Yes it is, there is 2 gray wires and two brown wires in the radio harness. What year blazer??? One of the brown wires is a spearker wire, and the other is the dimmer wire. The gray is illumination. disconnect both of those wires andtape them off seperately. then start checking fuses. the speaker wires will usually bw a smaller wire than the others.

 

It's a 91 Blazer, and I did leave those unconnected. I used a AA battery to test the wires to see which went to what speaker and such, and they are all hooked up right. Not sure, I'll be taking it out again and double checking.