I have a 2004 Impala. If you use alternate power source, the gages start jumping up and down, there is a thumping beating sound that comes through the speakers & then the battery is dead. Takes a long time to restart when jumping the battery. Also have had issues with high beam lights - all the car lights go out when the high beams are put on. Turning the car off and restarting immediately doesn't resolve the issue. It has to be turned off for quite some time for the regular beam lights to work again.