I have an '88 Trans Am. All the lights were working fine last week, but then I didn't have any dash lights the last time I drove the car. Thanks to some very helpful diagnostic steps from user Nina, I was able to quickly determine that there is a break/bad connection in the green wire from the dimmer switch to the 5A fuse.

So what's the best way to fix that? Ideally, I'd like to get a replacement harness from the dimmer plug to the fuse box. Any idea where I could get that, or how hard it would be to change?

I could just cut the wire and solder in a replacement, but that's a bit risky becuz I don't know where the break is. For example, if it's right at the connector to the fuse box, soldering in a new wire wouldn't eliminate the break.

It also seems strange to me that the wiring would fail like that. How do I stop other wires in that area from doing the same thing?

 

same problem here; it turns out the green wire was disconnected at the headlight switch. Matter of fact; all of the wires going to the headlight switch were "melted" into the connector on the headlight switch. I went to the pick-a-part yard to get another connector and it was melted also,,,just not as bad as mine. Pull your gauge cluster,,kinda easy... and look at the headlight switch connector. You would be very mad if you ran a new wire only to find out that it was messed up at the switch itself.
May not be the same problem; but you will have to get to the switch to replace the wire anyway. Also; my rheostat that controls the dimmer function was completely "fubar". If the wire is still connected the rheostat may be toast,,,same problem...
Open-circuit..

 

Yeah I had to take the headlight switch out to diagnose it, and nothing was melted. The dimmer wheel works fine too.

What I discovered is that the wire coming out of the dimmer is green w/ a white stripe, but the wire going to the fuse is solid green. So there must be a junction somewhere, and I'm assuming that's what failed. My guess is that the junction is in the big harness bundle under the dash near the steering column. Rather than tear that apart, I'm just gonna jump a wire from near the switch to near the fusebox.

 

So I started to jump a wire from the switch to the fusebox, but a thought occurred to me -- if that junction failed, there may be a short at that point. So before I soldered the new wire to the fusebox lead, I took an amperage reading. It was about 2.2A, so it was well below the 5A fuse on the circuit. So I finished soldering and the dash lights are working fine.

But as I was checking the dash lights, I noticed smoke was coming out of the headlight switch area! So I turned it off. I couldn't tell for sure if it was coming out of the headlight switch or the dimmer switch.

So is it possible that there really is a short at the green-green/white stripe junction, and it just didn't show up until I moved things around? In that case, all I would have to do is cut the original wire at the switch and at the fusebox. But before I do that, I want to make sure it isn't some other problem. What else should I check?

 

Was there a conclusion ? My gauge lights don't illuminate

 

I can't believe I forgot to update this post... anyway, I think what ended up happening is that the switch failed and caused a short, which in turn was responsible for screwing up the wiring junction. I bought a used switch on eBay and ran the jumper wire I mentioned earlier in this post, and that fixed it.