I've had my 2005 limited roadster for a couple of months now. When I got it I had no audio out of the right side (either door or rear speaker). After some troubleshooting I discovered that my head unit was outputting DC on the right side, so I picked up a Blaupunkt St. Louis of Ebay and installed it. Everything worked great for a week -- sound was fine out of the right side. But then it started cutting in and out on the right side again. This time it would emit some high pitched screeches and pops out of those speakers. When a fan would turn on in the engine, it would sound like a dentist drill or something like that.

So I figured that the original head unit had damaged the factory amplifier because of the DC output, so I just picked up a replacement amplifier off Ebay. After installing the replacement factory amp, I'm still having the same problem -- the right side cuts out with some high pitched screetching and popping. So I still have a problem with a new head unit and a new factory amp.

I've ohmed out speaker connections and they seem fine. Could this be a problem with the speaker? When the sound goes out on the right side, it goes out in both the door speaker and the rear speaker. That seems like a problem with wiring before the front/rear signals even get split going into the factory amp. What else should I look at to troubleshoot?

Am I risking damaging the new Blaupunkt head unit and amplifier with this problem?