Hello, I have a 1987 firebird with dash lights that won’t seem to work. I have replaced all the bulbs so I know it’s not that and all the other lights including, interior lights warning lights and pop up headlights work so I’m sort of confused as to why they aren’t working. I’ve checked all the connections with a meter to confirm they show continuity and made sure everything makes contact. At this point I suspect it to either be the rheostat or that white square thing above the switch which has two wires at the back of it. Any advice would be much appreciated thank you.

 

Most likely the "dimmer module". It's a transistor mounted on a heat sink. Not sure what transistor the factory used, butt a 2N3055 works great. Widely and cheeeeeeeeply available wherever electronic DIY parts are sold. Your local electronic distributor, TV repair shop if there's any such still alive in your town, MicroCenter and such, Digikey or Mouser or Jameco, ebay or Amazon, etc.