I just bought an 88 C4 Convertible a couple of weeks ago and the factory Bose head unit had been replaced with a Pioneer. The previous owner had installed it himself and had bought the wiring harness adapters so that it was just plug and play. My problem is two fold, first the previous owner was killed in a motorcycle accident about a year and a half ago and I bought the car from his widow after it sat for a year and a half in the garage so I can't ask him any questions about the install. Second there is a constant hissing sound coming from the right front (door) speaker and the left rear speaker. It stays at a constant level and is present with or without the engine running and is loud enough that the radio has to be turned up beyond a normal comfortable level to drown it out. I have opened up the dash and took a quick look at the wiring and nothing is loose or appears to be shorted so my next suspicion is the factory amp has issues. Does anyone have any ideas for checking and/or fixing this? I have moved speakers around and the hissing sound does not follow the speakers. I also noticed I have power going to both sides of the speakers which really seems odd to me since they are marked + and - I have installed a few radios over the years and never had power to both sides of the speakers. Any ideas?

Thanks,
Chris

 

Sounds as if the output from the pioneer is also being amplified by the bose amps. You will have to run resistors or bypass the bose amps and wire the speakers directly to your radio.