| Ok so I recently installed a head unit in to my friends car. Previously he had a really crappy Koss deck and only 1 speaker was working, the driver's side.
Well I put in a used deck I grabbed from CCA Forums and it powered up but only sound came out of the passenger's side speaker (no speakers in the rear), so that's really weird.
Well after a minute, NOTHING came out. The deck powers up, cd plays, tuner works, but no sound comes out at all. We are getting 12 volts between the ground and power, also between the ground and accessory.
I installed 2 new speakers in the front, using the factory speaker wire, and still nothing.
I made him go out and buy a brand new deck, low and behold, NO SOUND.
So anyways, after trouble shooting for a few hours, can't see any breaks in the wires etc, i took out the deck and hooked it up to a battery in my garage, hooked it up to speakers and BAMMO it works like a charm.
So I bring it to the car and it works with an external battery hooked in to the speakers in the car, so the speakers aren't the issue ( i don't think?? ).
We ran power wires directly from the stereo to the factory battery, again, no sound but it powers up. So i unhook the negative cable from the batter, no sound, unhook the positive cable from the battery too, so only the power and ground are direct from the deck to battery, and it works again!!
As soon as I touch either the positive wire (from the car) to the battery, the stereo stays on, but sound shuts off. If I touch the negative wire (from the car) to the battery, the stereo stays on, but sound shuts off. This is all while having the power and ground go directly from teh deck to the battery.
Does anyone have a clue what could be wrong? It really makes no sense to me. The head unit clearly has power and ground. My best guess is that something in the car must be shorting out as soon as i put the car's wire back on the battery??
Any help would be greatly appreciated.
Thanks.
Craig G | 
