unregistered user

Car is a '99 a4 1.8t. I installed a new amp and speakers and now I get a whine from under the right rear seat near the fuel pump when the engine is on. At first I thought it was the amp itself so I was worried about the amp ground. The amp ground is about 3 feet long and bolted to an unused hole under the seat and is about .9 ohms resistance to the battery negative terminal. Anyone ever have this problem?