My V6 mustang had what seemed to be a dead battery now I think it may be the battery as well as the alternator. I had to jump it off, shortly after disconnecting from the other car my mustang would stay running. The lights seemed to deem and then it would just stop. I pulled a battery from another car to see if I could get it to run long enough to get it home. It did. I tried to charge the old battery but the charger said it was bad and would not charge it. My questions are. 1. In the past regardless how dead a battery was I was able to keep the car running. I have even disconnected the battery and the car would stay running. (I have not tried to disconnect it in the mustang yet) 2. Is there a way to test the alternator without taking it out of the car? 3. The alternator looks pretty easy to replace. The single belt design concerns me a little are there any tricks to replace it if it comes to that?