Weird head unit issue

[Joshex]

So My girlfriend has a 2000 Honda Civic EX with aftermarket pioneer 6.5"s in the front, run off the head unit, and infinity 6x9s in the back ran off an MTX 4 channel amp. As for the head unit she used a Kenwood Ez500 for a while and when you hooked yellow (12v constant/memory) it would cause the car to have a parasitic drain and her car would be stranded often. I did all necessary testing with a volt meter and a test light and I found the unit would pull more milliamps then it should. I ended up not caring and just hooked the 12v to ignition, so it wasn't retaining information and the battery never drained after that. I then came into possession of a newer Walmart Kenwood unit (no idea what model, didn't look). So I went back and connected the wires correctly for the new unit (I thought the old unit is what was causing it). So to be sure I checked with only a test light this time (no MM here) the light would light up and when I disconnected the yellow 12v it would turn off. I tried running and external wire to it straight from the battery to see if there was an open circuit some where and it still would illuminate the light. This is where I'm at a total blank. I know my wires are all correct, I check for blemishes in wires on both sides of all the harnesses in view and as far I could tell, nothing. Is there any suggestions out there? Could it be one of my harnesses?

[Joshex]

Found out it was the harness.

[Ralphhummerh3]

usually the wires in the harness are bad