I recently had an aftermarket touchscreen stereo unit with GPS installed into my vehicle. Just noticed that when the unit is turned off that a slight humming noise emits from the speakers. The level of the noise increases slightly with any sharp increase in the engines rpm's. I only have had the car for over a year and as such I dont recall if this noise existed before the unit was installed.

Is this issue common for 997's or is it simply poor installation of the new stereo unit?

 

997.1s, this sounds like an installation issue. When the stereo unit is turned off, you shouldn't hear anything from the speakers. Do you have the Bose system and did your installer use the NAV-TV Most HUR interface for your new stereo unit? If so, I'd recommend having you installer check your system. If the radio is turned off but you're still getting noise through the speakers, then there's still power/signal getting to the speakers. The NAV-TV unit allows you to keep your car's original Bose amp and speakers, so it's possible the Bose amp isn't turning off when your stereo unit turns off. There could also be some other electrical gremlin going on, but you shouldn't be getting the humming noise through your speakers with the stereo unit off.

 

Thanks teejerdude. Car is coming out of storage soon, I will look review this matter again with your comments in mind.