I just changed out my alternator and got a battery last week. We can jump the car and the car will drive. While I was letting it just sit to run to charge more the car cut off and nothing happens. When the key is turned, no lights no nothing. Its like the bad alternator drained my battery to nothing.

What could it be?

I just hooked battery up a charger to see if new battery is culprit.

  • 3
    That sure sounds like a dead (or disconnected) alternator.
    – zipzit
    Apr 25, 2016 at 23:22
  • 1
    Bad battery connections is most likely.
    – Moab
    Apr 26, 2016 at 22:48
  • Did the car charge? Apr 27, 2016 at 4:30

1 Answer 1


Is the field coil connection connected? If not the alternator will not produce any output at all. The field coil supplies the magnetic field needed to induce current in the alternator coil winding. There are 2 connections on a alternator. B+ Output of regulator Field Field coil connection The ground is the casing of the alternator. The plug for the connection is white with 2 wires, one black,one red. The plug is polarized if I remember correctly so it only goes one way. When you were driving your battery was powering everything.... Once the battery voltage drops below about 9-10V it will not engage the starter. If you keep driving the battery keeps draining past 7.5V everything related to the engine like the ECM starts shutting down. Even further the lights quit.

  • To add to this the field wire is just a fused power source. I think the fuse is in the underhood fuse box.
    – Ben
    Apr 27, 2016 at 23:02

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