1991 Roadtrek Battery Isolater Hookup

Below is question I sent to the techies at RT and I did'nt get the answer I was looking for.

I recently sent a question on the battery isolator hookup on my 1991 Dodge B250 Trek. RT's response was to tell me what the standard hookup is, which I already know. The problem is , I still don't know what the wire is thats comming out of the firewall that is green and turnes into black. The alternator output red wire is currently directly connected to the battery + connector. That red one should be connected to the middle terminal on the isolater. I dont know if that green-to-black wire is supposed to be connected to the primary battery side of the isolator no1 terminal. Seems like there has to be a wire connected to the engine positive terminal side of the primary battery.
I need to know what the green to black wire thats coming out of the firewall and where its supposed to be connected to. The puzzling thing is that it has current (its hot) with the motor off (no alternator) while it is not connected to anything.

Anybody that has a older 90's Treck may be able to help me.

Re: 1991 Roadtrek Battery Isolater Hookup

Don't know wich style you have. If it is the block style, the alternator wire hooks to the center, Primary battery wire on the left terminal and secondary battery on the right terminal. If its just a solenoid style there is no alternator wire. A wire runs from the primary battery to one large terminal and a wire runs form the secondary wire to the other large teminal then a small wire runs from a hot when key is on terminal to the small terminal on the solenoid. If you have the block style that wire may be the Battery charge wire of your harness.
Re: 1991 Roadtrek Battery Isolater Hookup

Thanks for that info, it is a block style. I guess I'll need to figure out which one is the main alternator charging wire and connect it to the center post of the isolater.
Then connect the other wire to main battery. If that checks out, then connect the house bat to the aux post of the isolater. If that doesnt work , I'll need to go under the dash and figure out excatly where the 2 wires comming out of the firewall originate.