My stereo keeps dying. HELP!

[scott s]

 I've lost four stereos to what the repair shops are calling "moisture damage". I lost another one today and am at my wits end. Read along:
 
 When I replaced the carpet in my '70 I ran wires front and rear for a new stereo system. I installed the speakers and paid a local shop to install the CD/tuner. It lasted for a month or so until it sat outside at work during a TORRENTIAL downpour. When I got in the car it was dead. Took it to the shop, sent it back to the manufacturer and they said nothing was wrong. Reinstalled it and it worked fine...for about two weeks until, you guessed it, another strong rain storm.
   I asked the shop to check for evidence of water, cables grounded, etc. They found NOTHING. All wires properly hooked up, speakers checked out fine, no moisture damage anywhere.
  Sent it back, the factory claimed moisture damage and repaired it. I purchased a different deck, installed it, drove around for a couple of months. The car sat outside overnight at work, it rained heavily all night, got in the car and noticed that the radio was powered on and humming even though the key was still in my pocket; ignition off. Took it to the shop, moisture damage, not covered by warranty.
 I purchased a used Marine radio (only one I could find with a black face). It was faulty from the get-go so the shop gave me a loaner. It worked fine until today. We had a strong band of thunderstorms come through. I got in the car and noticed that some of the faceplate was lit up...I knew right then what had happened.
  When I got home I got under the trunk with a flashlight. I see NO water or evidence of water anywhere. The ONLY place I saw a drop was at the end of the drain tube for the fresh-air box, but it's supposed to be there. I looked back up under the cowl, around the wiper motor, fresh-air box, fuse-panel....everywhere. Not a drop. It doesn't appear that the radio is/was wet either. I unplgged the head unit from the fuse panel and plugged it back in, but it's still dead....just some background lighting on the faceplate, no functions.
  * NO water that I or the stereo shop has ever found.
 * All speaker wires and power wires in good shape and tested for grounding, etc...all fine
  * All rubber/weatherstripping on car is intact and in good shape
 
 I have washed the car dozens of times with no problem. I have driven in the rain dozens of times with no problems. It only seems to happen if there is a HEAVY rain and the car is sitting outside.
  HELP! What do I check next?

[az67calbug]

My guess is you are going to have a short in a wire someplace. It's either going to be a remote wire, or a power lead wire.  A wire that is going to have juice to it.  Since you mentioned that you didn't have your car turned on, but the radio was on, I bet it's going to be somewhere near the radio.  It has to be shorting out somehow.  The water is touching a wire and grounded it to the chassis. 

You might want to also check that they didn't "Staple" your carpet down... or under your carpet the wire is frayed or damage.  Water getting down there can also do it. 

If I were you.. I'd rewire the entire system. And park in the garge durning rain!

[scott s]

I wired the car (inside the cabin) when I replaced the carpet. I 'pretty' sure there's nothing going on inside the car. I'm waiting on a marine radio to come in stock and they're gonna check the wiring underhood then.