None of the dash or gauge lights in my 1980 240 are working. I have checked fuses and looked for shorts in the wiring, but I can't find any. I think the **** to control the brightness might be bad, but I'm not really sure how to check. Does anyone have any suggestions?

 

It's really simple to test the dimmer; they do die. Pull the switch and on the back will be 2 contacts, one may actually have 2 spades on it. That will be the outgoing current. Use a test light and see if you have current to the switch by turning your lights on and putting the test lights lead to a reliable ground. Then do the other connector...no juice coming out but juice going to it would indicate a bad rheostat. If you don't know, the right hand side parking lights are on the same circuit...so make sure they are burning.