I just got a 91 E150 off of CL. Everything seemed to be fine, until I went to drive it at night. When I turn the headlights on, the radio display cuts out completely. No dash lights or rear running lights. The only map lights that work are the two up front. And the rear "rope lights" or whatever, over the seat/bed don't work either.

I've replaced all the fuses and even tried swapping out the headlight switch.
I tried swapping the switch because I somehow managed to get the dash lights to work for a second or two by holding the headlight switch between off and on. Replacing it had no effect.

Any help would be amazing. Thanks!

Oh, and this van has a CB/PA, radar detector and tow package installed. Can't hear anything out of the CB/PA even when playing with squelch. Also the toggle switches above the rearview mirror (whatever they are supposed to do) don't seem to light up either.

Thanks again.

 

You might start with removing the rear tail light lenses or remove the plugs from the inside of the vehicle if accessible. I think you may find the problem with one of the tail light plug wires.
Don't forget to check the towing plug wires too.