Thanks in advance to any replies, This is my first post on here. Ive been having problems with interference from my speakers (Passenger side only) I get a hissing sound intermittent even when the car is switched off and the stereo unit off. A guy i know tested the rear speaker and it was dead although he check the wires to find 12V was coming through. I managed to get another speaker and connect that up to the right side wiring bypassing the other. But i am still getting this intermittent hissing through the front door speaker. Any suggestions as to what it could be or what i should start checking?