Hey Randy
We see this problem all to often. If you can tell what wire is the ground for
your new radio make sure it is not hooked to the gray and blue wire of your
radio harness. Radio shops use a test light to look for there power and
ground points and when your lights are off your dimmer reads a ground but
when you turn your lights on POOF!  there's power.

Jeff E.   Lilburn, Ga.
87'WESTY Weekender (BOXOBLOX)
87'GL