Hi all ive got a bit of a problem with my radio, It works just fine until I start the engine then the sound stops and the display goes dim but still readable. Its very odd because Ive used a meter to check the voltage and it seems to be once I start the engine and the voltage rises, at about 12.7v the fault occurs then if you turn the engine off once the voltage drops back down at about 12.2v the display comes back on full brightness and the sound comes back on?????