Just got a 1979 Bronco with factory dual batteries. Lots of other options too but the dual batteries are giving me fits.

Previous owner seems to have disconnected the dual system. Found a wire that has a fusible link on one the end of it just hanging down below master cylinder. Below the junction stud on fire wall. There is no power to this wire in any ignition position. This wire also has a female connector on a 6" wire integrated with it that is not plugged to anything.

Aux solenoid has a positive (red) cable that goes from aux solenoid to positive battery terminal plus a female connector that is not hooked to anything. The other side of aux solenoid has 1 wire hooked to it and that wire goes to dash just after splitting and going under vehicle toward rear.

If I hook the wire that was dangling down, not hooked to anything, to the junction stud on firewall I get power on the single wire on load side of solenoid. Problem is this unhooked wire will also reach the solenoid so I do not know where to hook this wire. To solenoid load side with 1 other wire or to the two wires already hooked to junction stud.

My common sense says hook to junction stud because its obvious that the wire on load side of solenoid and the dangling wire are connected somewhere and I ASSUME main battery power has to reach aux battery somehow to charge it?? Right?

Does anyone have schematics or an idea as to how all these wires work together. Broncos have lots of wires to the main solenoid one of which operates the rear window. But this bronco has 3 fusible links on battery side of main solenoid and at least 3 more between the main and the aux solenoid maybe more.

Not 100% sure the solenoid is working correctly either. I do get power from key to solenoid in AUX1 AUX2.....I hear loud clicking. It also clicks when put in crank position than clicks again after done cranking and in run position.

Bronco is a Trailer Special edition so I think most of the aux battery load side went to rear of vehicle for a camper.
Any help would be greatly appreciated.

 

Neverminded all.

I found a schematic tells me all I need to know. Hope it helps someone in future.
wiring_79master_1of9.jpg (2766×1688) (fordification.net)