- Reaction score
Difficult to tell for sure without diagram and/or pics, but it sounds like you connected things up right. You're lucky the wires were well labeled! And just to confirm, the short heavy black wire would go between the negatives on each battery (see Denise's drawing above). And it doesn't sound like you did anything wrong operations wise. It sounds like the alternator was powering things when you shut it down. My first guess would also be a bad battery switch.