Started putting the fresh center console parts in my wife's '84 (thanks, handymanpat!) and noticed something that made me concerned. There's a wire in one of the harnesses that has burned way back into the harness. I can't find anything in my Chilton's identifying radio wires (or the heat/ac wires), showing how far back I may have to chase this. To help eliminate what it ISN'T, it isn't in the heat/ac or fan speed switch harnesses, and it's not in the 4-wire 16 gauge (light blue, dark blue, brown, yellow) bundle (need to know what these do; rear/headrest speakers, maybe?). The wire in question is in the 7-wire 16 gauge bundle (light green, dark green, tan, grey, black, yellow and the burned one with a light-colored jacket). This car came to us with a poorly installed aftermarket stereo, and it has been troublesome at best. Can anybody help me identify the purpose of this wire and where it goes once it hits the main harness? Thanks in advance - Chris

May have just stumbled on the answer... two grey wires in that particular bundle. One is a front speaker negative, the other comes out of either the headlight switch or the dimmer wheel. My bet is it's the illumination wire that shorted to ground...

I am pretty sure it is from the headlight switch. It tells the radio to go in to "dim" mode when you have the lights on.

Can you post pictures?

Thanks, buddycraigg. You are correct, it's actually the grey wire out of the dimmer connector. While this thread is awake again, does anybody know for sure the functions of the wires at the dimmer? Pretty sure there's going to power from headlight switch, variable output to instrument lights, the radio output and possibly a full-on dome light power, but Chilton's wiring diagrams are so basic and patchy.

quote Originally posted by CSM842M4: Thanks, buddycraigg. You are correct, it's actually the grey wire out of the dimmer connector. While this thread is awake again, does anybody know for sure the functions of the wires at the dimmer? Pretty sure there's going to power from headlight switch, variable output to instrument lights, the radio output and possibly a full-on dome light power, but Chilton's wiring diagrams are so basic and patchy.

My question is, is the radio working correctly or are you blowing fuses?

Thanks, IMSA GT. Your question about the radio working comes with a long answer - the radio in the car when we bought it was a poorly installed aftermarket unit, but it did as it was supposed to. The factory unit in our third Fiero was obviously pulled out in favor of an aftermarket, but thrown back in when the prior owner put it up for sale (the mounting brackets are missing). So, the '84 SE is without factory connectors to hook up to the factory unit. However, to the best of my memory, we were not blowing fuses with the Sony stereo in the '84. I'm thinking of running a duplicate 16 ga. grey wire from the dimmer to the radio cavity, re-installing factory-style connectors, then either installing the Delco radio or using a proper wiring adapter for a Kenwood or Alpine unit.

Sometimes that grey wire creates major issues. The most common is that you turn on your headlights which activates the dimmer. The fuse blows which controls the down motion of the headlights as well as all of this:


So if you hook up the grey wire and the above list suddenly stops working once you try to raise the headlights, you'll know to disconnect the grey wire.

[This message has been edited by IMSA GT (edited 03-17-2022).]