Alternator whine when lights are on

[Strider]

I have a blaupunkt hu, Pioneer 5 channel amp system. Twisted pair shielded rca's run down the driver's side of the car to go to the amp, the power supply for the amp is on the common bus where right by the battery, then runs down the passenger side of the car to the trunk. I don't recall exactly what ground wire I used for the head unit, but the amp has a short ground strap in the trunk. The whine is only apparant when the running lights / headlights are turned on, and is present independent of the volume setting of the head unit. Bad ground on the amp or HU or both?

Thanks

[Ashman]

I would try regrounding the radio and the amp. I would also check to see if the speaker cabling is running too close to the power wire.

Sounds to me like there is a ground loop somewhere.

Alon

[Elecmech]

Agree, the ground point should be as close to where the ground connection from the battery connects to the chassis to avoid voltage drop's in the ground connection when a large amount of current flows. In Elec Eng terms this is called "star-point" grounding. (In some stubborn cases we had to isolate the amp from chassis and use a separate ground cable to the bat -ve pole)