Hi, I recently did a cluster swap. In order to make the swap clean looking, I need to wire in the 90-91 dimmer switch into an 88-89 harness. I have the 88-89 dimmer switch with integrated brightness control box, and I have the 90-91 dimmer switch. A few questions...
1) Where is the 90-91 brightness control box located on the EF chassis?
2) Can I just desolder the physical switch inside the 88-89 control box, and solder on the wire ends from the 90-91 switch?

ANY sort of guidance is helpful... It's been bugging me for a long time...

 

On my 91, the dimmer is a separate unit in the dash. It controls the ground side of the cluster bulbs (and heater panel, stock radio, and cigarette lighter if equipped).

The dimmer is not a simple switch or rheostat. It is actually an electronic module that drives the ground wire with pulses. The brighter the dial is set for, the longer the pulses are, thus the brighter the bulbs.

I think the red and black wire is full battery voltage when the lights are on (connected to one side of the bulbs) and the solid red is the variable ground (connected to the other side of the bulbs).