Cluster lighting

[Devin]

I'm having issues with the backlighting for the cluster. When the dimmer switch is clicked to the On position on a 90, are the circled bulbs supposed to be getting power? In this picture I have it clicked on, and the key is in the On position (engine off).

I verified that fuse 4 is good. I got light to the glovebox, and these ones are lit up, although I'm not sure if they are on the same fuse or not.

 

[Devin]

I got my hands on the wiring diagrams for the car and turns out that the issue is the rheostat. I directly jumped the wires and got 12v then tried the lights and voila.




So, anyone know if the rheostat is rebuildable, or do I need to find a used one? I tried my spare but that didn't help (which led me down the rabbit hole).

 

[Devin]

Also, I broke the tab for pin 1 on connector A (the one for the illumination). Anyone know the part number for that?

 

[Irish Pride]

I don't think the cluster lights are supposed to come on with the dimmer. They come in with the headlight switch in the on position and with the auto lights on and it being dark enough to trigger the light sensor. The dimmer switch just controls the interior lights. Overhead, door panels, and kick panels.

-Chad

 

[Devin]

The rheostat controls the brightness of the cluster, so I'm pretty sure they are necessary. I could get full brightness by jumping it, but I'd like a functioning dimmer.

 

[Devin]

Found one new on Ford Parts Giant. $54 isn't too bad, I guess.

 

[Devin]

New instrument dimmer is on its way. We'll see if this fixes the issue.

 

[Devin]

So I replaced it and now the dimming works. But then I noticed it wasn't working again and then this:

 

[zoomlater]

did you pull the headlight switch yet to check the connection? wasn't there an issue with the headlight switch going bad

 

[Devin]

Yeah, the harness was tight. It is definitely the switch.

 

[Devin]

The new switch fixed my cluster lighting and my lack of running lamps.

 

[Devin]

The SHO is drivable again! Now I just got to get tabs for it and I can see if there are any other problems.

One quick question for those in the know: I noticed that the fuel gauge and temperature gauge colors don't match the tach and speedo. What years came with which color gauges? Mine (90) seem a bit more green and the replacement cluster I got for the fuel and temp are more white or blue-ish.