The needles don't do the "full sweep" that I've read about which would indicate a bad battery, alternator, or both. When I turn the truck off, all of the needles move to zero (including the tach) but the tach then returns to 1900. Once I put the key in and turn to on, the tach moves to zero. If I start the truck, the tach shows normal operating RPMs until I turn it off, which it will go to zero and then pop back up to 1900 with the key off. The truck is running just fine and all seems well. Weird. 01 HD w/ 122K miles.