The batteries charge through the normally closed contacts on one of the speed contactors (third speed I think but it has been a long time since I worked on one of these) If you put it on charge and slide the normally closed contacts around you might detect sparks or a change in the charger hum when you get to the bad contact. Don't mess with the F or R contactors unless the wheel is off the ground. It can still run with the door open. The speed contactors are on the right side.