So I’ve got this 1994 E350 Motorhome that I just picked up. Brake lights work fine, Turn signals work fine, Tail lights do not work. Front marker lights work though. I replaced the dash light switch and checked all the fuses. The fact that the front marker lights work is leading me to think there is a broken wire going to the back lights. However..... Ith the key on (truck running or not) the tail lights are dimly lit up. As soon as I turn on the headlight switch they go dead. Anyone run into this issue before? I’ve never had tail lights dimly lit with the key on before.

I ordered new tail light housings and bulbs and will be installing them this week (just because I know they need to be updated anyway). I am prepared to run new wire from the tail lights up to the front but I’m not exactly sure where I am going to tie it in at.

Check to see how much voltage you have on the tail light circuit at the sockets. That would be a good start. Need to check for high resistance and check your grounds as well. A visual inspection of the rear wiring can find broken or damaged wires that may be causing the issue.