1) Following up on the ground question, is the second battery ground run to the truck body or does the ground just run to the primary battery -- that is, do you have no ground connection when the second battery is isolated?
Maybe. I don't know that isolator, but if it's isolating both the positive and negative, that's the problem -- seems strange that it would, but without seeing it I can't think of any other reason it wouldn't work when the batteries are isolated and the positive is direct to the battery. With the battery isolated and the lights on just touch a wire from the aux. negative to ground and see if the lights go on -- if so, it's a ground problem at the battery. Maybe someone else will weigh in, but if that's the issue I don't see any reason that you can't run a ground from the aux. battery to ground in addition to the primary battery -- you can get short 0/1 gauge cable for that.
You said the switch runs a relay. I would check for power at the relay. Is there power going to the power side of the relay - should be power there under all battery scenarios as that is direct to the battery? Is there power going to the switch side of the relay with the cap light switch on - if it's not keyed power it should be powered under all conditions if the switch is on?
Wait, I reread your first post. I was thinking you were just talking about it not working when the battery is isolated using the TrueAm. But you are talking about disconnecting the aux battery by disconnecting the Andersen Connector. If the only ground goes to the Andersen and if you disconnect that you are disconnecting the ground on the aux. battery. So yeah, that's the problem. If you want to disconnect the Andersen and still use the battery, you're gonna have to have a separate ground from the battery to the truck -- you can still have the ground go to the Andersen so it connects to the main when it's attached, but if it isn't separately grounded to the truck it isn't going to do anything when the Andersen is disconnected.
Where are you getting 12.7 volts connected and disconnected? Are you simply checking at the battery posts?
Shouldn't be a problem. Ideally you want a good 0/1 gauge ground cable. Local auto supply may have something that will work. There's also a guy in Duluth that makes them to size and termination as requested on eBay -- see here. Not sure how close that is to you, but shipping is free.
As i think about this more, this is still puzzle. The anderson connectors disconnect the second battery positive and negative. that said, the topper light wire is connected directly to the positive on the second battery...which goes back to having to track the grounding of those lights.
I work near duluth. I have plenty of 2 gauge left from the battery install. Thx for the help.
Yes you can and should. It will still disconnect with the Anderson, but still be grounded so that anything with the positive connected to the battery will still work.
Nope, as Hotrod indicates below, you are removing the ground for the battery when you disconnect the Andersen. Think of it this way. You have to have a complete loop from the battery positive back to the battery negative to create a circuit. The most basic circuit would be: (a) Battery + terminal, (b) a wire going from battery + terminal to lightbulb wire in, (c) lightbulb filiment, which lights up, (d) wire going from lightbulp wire out to out to Battery - terminal. You have a complete loop from Battery + to Battery -.
