High Pitch Whine From Amp?

Ok, so I bought a used Crescendo BC3500D and had it shipped up to me when I was at school. A friend had a variable voltage power supply so I checked to see if the amp was working while up there and everything worked fine. I then took the amp home with me for this Thanksgiving break, hooked it up in my car, and the second it gets power, the amp gives off a constant high pitch whine. It sounds like coil whine, if you've ever dealt with that in a PC before. It doesn't matter what the gain is set at, what's connected, or any settings on the amp. My gut is saying my ground is the issue, simply because it's a seat bolt. There is nowhere I can ground my amplifier in my trunk other than that bolt due to the way the SUV was designed back there, so I'm stuck on that ground. Do you guys think that could be the culprit? Any insight would be great, thanks!