Gage lights not working properly. 1990 Ford F-150. Dimmer switch?

[blackbronco92]

1990 Ford F150 XLT Lariat. I am working on this truck for someone. They installed the CD player improperly and blew the gauge illumination fuse. Fuse has been replaced, and I have checked every fuse in the truck, all are good.

All electric works, including the (reinstalled properly) CD Player. The guage lights will now ONLY illuminate when the dimmer switch is turned all the way to the left, after the clicking point. (The dimmer is all the way to bright, and then it can click one more time causing the dome light and cargo light to illuminate) With the switch in this position is the only way for the dash to illuminate.

Any idea?
The headlight switch is a pull type, 2 notches are used, the first notch is for the parking lights, and second activates headlights. This same knob is also the dimmer and so turns from left to right. With either parking lights or headlights on, the dash does not illuminate unless the dimmer switch is ALL the way to the left, but this position allows the dome light and cargo light to be on as well.

 

[Firestormer]

Sounds like when they blew the fuse, they caused an open circuit in the pot that dims the lights. You can either buy a whole new part (probably expensive if you can find one) or you can move the wire for the instrument lights from the pot to the switches parking lights output. The gauge lights will come on when the parkers are on, but they will be at full brightness all the time.

 

[Zimmer]

Is that not what is supposed to happen.