Lighting Nightmare

I posted more detailed info about the light wiring in this thread http://forabodiesonly.com/mopar/showthread.php?t=83686

Maybe that will help?

Not sure exactly where you are checking with the meter, but my hunch is the problem is either in the fuse box, or bad grounds somewhere. The way the park/turn signals and the tail/brake/turn signals are wired, the two circuits share a ground connection, and can do weird back feeding thing if the sockets aren't getting good grounds.