When I move the dial up or down, nothing happens at all except it turns the dome light on when Im inside the car, but it dont dim the interior lights under the gauge cluster. Whats wrong? How do I go about fixing this problem? Thanks, any suggestions would help. I have the 86 T/A with the mechanical gauges if that helps.

 

Exact same problem im having, hope someone knows...

 

Had the same problem. Found severe oxidation on the reostat part of the switch. Caused constant voltage to the lights. Try a new switch they're cheap.

 

It's a little tricky to change. You can pick one up from autozone for less than $20. A manual that shows how to remove the old switch will help.