I just picked bought my '90 GT. I have noticed that all the lights outside the car work when I hit the light switch but the interior dash lights don't come on. And also the radio goes blank to when I turn on the lights. I have checked the fuse and all is good there. I have thought about maybe it is the dimmer switch....any ideas?

 

You have a good thought. My dimmer switch has bad spots in the stroke where the dash will go completely dark. I've read several posts where these go out. Might try rapily moving the dimmer back and forth and see if anything changes.

 

I've tried that no response....anyone know how to check them?

 

You could pull the switch and check the resistance across the poles with an Ohm Meter. As the switch goes brighter the resistance should go lower. I suspect the resistance will be high or infinite showing an open circuit.

 

I have the same problem I'm in the process of caseing it down and will let you know what I find.

 

My ranger has an issue where the dash lights don't work...until you twist the ****, which is the dimmer in the main light switch, so you may check that switch. First things first, check power coming out of that switch that is the wire for the dash lights, if nothing replace the switch

 

It was the dimmer switch. I jumped the lb/r (light blue and red) wire to the brown wire and the dash lights are on full bright all the time. The only downfall is you can't turn the dome light on by the dimmer switch. But that is a good temperary fix

 

Ok my 91 GT is having this issue but I keep blowing the 5amp fuse in slot 13 the dash light fuse. I don't know if the lights work or not because each time I replace the fuse and try to turn them on I pop a fuse.. I assume this is a switch? Would it be the square switch that actually turns the lighs on or would it be the dimmer that you move from left to right? Thanks.

 

by chance, are all of the wires to the radio correctly insulated? There is a wire in that hrns that is often not used, I have seen hacks install radios and just leave it uninsulated and it grounds out and pops the fuse.

 

This problem has to be endemic of this model, I have the same issue, I have unplugged all the components from the harness and using a meter I get a ground condition at every location with the light blue with red stripe wire. I even unplugged the illumination relay. Has anyone ever discovered where this wire goes to ground on the 87 to 93 Fox Body?. Since I have removed the headlight switch, dimmer, instrument cluster, illumination relay, radio and heater control light from the equation It has to be in the harness. No amount of pulling or jiggling the wire harness makes a difference in the grounding.