I suspect your problem is the ground inside your head unit; I've just fixed your empeg unit and this was the problem.

What happened was the loose wire touched the case of the empeg (and your head unit, it looks like) and tried to short +12v through the case to ground.

If you don't want to send it back to the manufacturers, I'm willing to take a look at it - but you'd have to send it here first.

Re: the test meter, on resistance it should measure very near zero if the wire is ok.

Hugo