Car Stereos: car audio problem, original radio, circuit city

Question
The original radio in my 97 Subaru went out a year ago so I replaced it myself with a Sony aftermarket and new speakers. Everything was fine for three months then sound quit. Circuit City tested on their speakers and said there was no sound at all.   Replaced radio again and bought extended warranty this time. Everthing was fine for about 4 months and sound quit again. I didn't do anything about it for a couple of weeks and eventually radio would not power up at all. Circuit City sent out for repair, but was not repairable so they gave me a new one. The third radio worked good for two weeks then sound quit. Radio also will not tune (which you can tell by display). Circuit City says I may have a short in my wiring. I've checked all wires that are not hidden and all looks okay, as well as connections. My question is: Is this probably an electrical short? How do I find it, or do I have to replace wiring? Would it most likely be in power coming into radio or in wires to speakers? How do you replace wiring? Is there some way around this? I travel a lot and need the stereo to work so I can listen to books on my MP3. I'm afraid Circuit City would want a fortune if I ask them to figure it out. Or they would sell me new speakers, tell me everything is okay and three weeks later I'd be in the same boat again.

Answer
Kerry, your problem does sound like an intermittent short to the speakers.  I have found it easiest to run new wires my own way.  Many times the factory wires are bunched together with other wires and taped up to make less mess.  The short is usually where the wires meet the door, either on the body side or the door side, they are rubbing.  Once you have your own wires run from the radio through the dash to the door jam, then you can remove the factory wires and run your new wires through the existing holes.  Be sure all sharp corners are covered.  There is a slight chance that one of the wires coming to the radio has a short as well, but not likely.  I would be sure the ground wire is connected securely to a good ground point, then check the other wires as far as you can.  That sounds like a very frustrating problem, but it does need to be addressed or it will continue.  Hope this helps, Scott