Added a new amp to my stock HU. Everything went fine until I started the engine. With the engine running I am getting what sounds like clipping from the rear channels. With the key in the acc. position I have no problems. Hooked up a bench radio to the amp and tried it. No problems with the engine running or in the acc. position. Replaced the line convertors and rca cables as a precaution and that didn't help.

I came to the conclusion that the problem is in the factory unit and only the rear channels and only when running. Anyone got a cure for this?