overcharge
The usual cause of this is heat in the bulkhead connection over time causes the female terminal to expand. Take the female connector out of the bulk head and squeeze it slightly. this should tighten it up for a better contact. Also while its out solder the connector to the wire. do the same thing to the male. They are pretty easy to take out. Male comes out with a side ways squeeze with a small piers. female with a real small screwdriver or pin pushed in on the little square opening on the one side.