I have a 1967 cutlass supreme and since I've bought it the dash lights will stay on even when the car is off. Only way to turn them off is to unhook the battery and that is getting old. I replaced the head light switch thinking maybe the dimmer was broken but that didn't change anything. Has anybody experienced this problem before. The lights don't dim at all with the switch either.

 

I think you need to pull the dash apart and start tracing wires. They are getting power from somewhere other than the headlight switch. Does the car per chance have an aftermarket gauge set? If so I'd start there.

 

I had a similar issue that was traced to a dash map light that had a manual on/off switch. The switch had broke and was permanently on, and that turned all the interior courtesy lights on. This was discovered after hours of tracing wires and trial and error.

Before tearing every thing apart,I suggest getting a wiring diagram and tracing it through, and testing the various components along the way. . Maybe something simple will materialize

Maybe someone hacked a wire for a radio power lead and it is shorting? Who knows what has been done to these 40+ year old beasts.

Good luck. These issues are maddening.

 

Yes, start looking for aftermarket equipment (gauges, radios, etc) and wiring hacks done by previous owners.
I bet a backlight in something was wired to the car''s gray wire for the dash lighting and also connected to constant power.

 

Hey guys thanks for all the suggestions. I had the dash apart before this and did clean up some odd wiring. I left the wiring for an aftermarket radio and I will go back and trace it all. I just installed a trio of gauges the other day but did not even hook up the lighting yet. I'll be working on it tomorrow and will report back.