2000 Bounder D.P. 39 Z house battery connections help

Is there by chance one coming off the converter for ground? This sounds fishy and modded.... You should be able to find a heavy gauge cable connecting to ground somewhere. Where does the negative cables go?

Forgot to ask, where does the negative lead out cable go to and have you followed that?

If the heavy wire leads in the general direction of the generator, that's a very likely destination for it. Generators are commonly connected to the house 12V system, and the generator starter motor uses a lot of current when cranking and so needs a heavy wire. 2 gauge would not be out of line. (My Onan 4KY generator uses somewhere in the rough vicinity of 100A when cranking.) RV generators also need a little bit of 12V power to generate, to power the control electronics and fuel pump and so forth.

There likely is also be a heavy wire going off to the chassis electrical system via an isolator of some sort to charge the house battery from the alternator while en route. It's possible that the same wire would be used for both.

I would urge some caution about relying on wire color to know which wires are positive and which are ground. It's nice when they're reasonable and consistent, but it's far from universal, particularly after various owners and repairmen have tinkered with things.

I don't know where your ground lead went from the factory. On my (completely different) motorhome, it just goes from the battery to a nearby bolt and nut on a chassis frame member. It was quite plainly obvious. The wire itself needed replacement when I got the RV (the connector was broken), but the routing to ground was in plain sight.

Chris,
Thank you for your response. Due to unknown history I traced all of the AWG2 cables and labeled each, then drew a diagram which includes the inverter/charger, the 150A fuse, the paralleling relay, and both battery banks. In case of uncertainty, I disconnected both ends of a cable and pulled it free to make sure there was not a hidden connection. Caution is definitely required due to the possibility of big arcs and blown equipment.
Thanks, John

John, you probably know this, but try checking voltages at the batteries, then fro + to ground. If all is good then start checking from the +s to ground until you find a problem. Have you started the engine? Sometimes starting the engine will cause a hung disconnect solenoid to latch in. Contact Fleetwood.com and they may be able to send you the electrical wiring, both 120 volt and 12 volt, for the house. If you can get the plumbing prints also.
Good luck

Jim,
Thank you for the reply. I will try Fleetwood.com. I think I just found an exact match at Camping World about an hour way.
Lance