Hell, you should be happy it makes wine. It might not taste like a fine wine, but anything is better than nothing.
Now if we are talking about whine, then you have a different story.
Seriously, this might be tough to track down. Could be the wiring or it might be the amp itself. It is definitely fixable. You'll just have to keep trying different things (bigger ground wire, RCA wires not running with power cables, etc). You could also try getting one of those alternator filters from radio shack if nothing else works. It should cut down on some of the whine and it is cheaper than buying a new amp. Good luck.