I replaced the shaker 500 in my Mustang with an Alpine and then sold the shaker. The person who bought it contacted me and said that with all 3 harness plugs connected they get what sounds like alternator whine. If they disconnect the subwoofer plug (8 pin next to antenna connector) the radio functions fine and the alternator whine goes away. I did not have this problem when the shaker was in my Mustang with all three connectors plugged in. Any ideas why the whine is occurring in the other person's vehicle?

 

Is the whine coming through the speakers or actually from the alternator? If its the speakers then its a wiring issue on the guys car. Most likely a bad ground somewhere in the audio system. If its the alternator, maybe its on its way out.

 

Yeah it's through the speakers. Bad ground is what I thought of too and told him to check them. Thanks.

 

Grounding issue is my bet.

They need to find the grounding points for their system and either move them or have them all terminate at the same point.

A cheap bandaid is a ground loop isolator at one or more of the ground points but it may only decrease the wine and not remove it entirely.