ELECTRICAL GREMLINS [OVERCHARGING 440-3]

Nice camper. I've got good news and I've got bad news. Good news ---you can fix it. Bad news--- you've got to fix it.
Your Truck has the isolated field type system. It should have a blue wire [12 volt with ignition key on], connected to either alternator field prong; It should have a green wire [the variable ground from the voltage regulator] pushed into the other field prong. The voltage regulator should have a triangle shaped plug pushed into it.

You have the wrong alternator. The alternator shown in post 6 is a grounded field type, even though one of the prongs looks like an electrical connector, it is NOT. I believe you can convert it using the kit from post #12. The 'wide prong' terminal is grounded; causing the alternator to overcharge.