My dealer rewired my battery cut-off switch 3 years ago because I could not seem to retain a charge. Then we replaced the batteries, although the dealer used type 27's instead of the 31's that were supposed to be part of the residential fridge option. Still no luck, so another shop rewired again, (again no luck). At the rally last year, RW techs rewired again. It seemed to be better, but now I still have a problem.
Today I pulled off the battery covers and disconnected the wires and noticed a 6 gauge wire going to the cut-off switch from the positive side and a pair of 1/0 wires, red and black. The black going directly from the battery to a hole in the bulkhead to the basement. The red going to a 2 pole connector block and then through the bulkhead hole. Presumably, these are going to the inverter.
These wires have a load when everything is off inside the RV. I'd guess about 10 amps continuous from the spark when I reconnect them. :ohmy:
I will post some pics when I can upload them. In the mean time, I'm thinking of rewiring the switch with a 1/0 red wire to the switch and then feeding the inverter with a 1/0 from the switch to the 2 pole connector block. The original 6 gauge red wire from the switch could then be moved to the block as well. This would let the switch actually control all the current from the batteries (apparently a novel idea!).
All advice would be appreciated. :S

Not sure what you mean by "retain a charge", but I will let you know my experience with the wiring set up in our 2013 36RL (without residential fridge).

The original wiring was set up so that the battery disconnect switch did not disconnect everything. From memory the level up stuff, the power to the front slide electrics and possibly the CO/Gas detector power was still on with the disconnect switch off. When I switched the batt switch off the batts discharged completely in a month or so even though the RW was plugged into shore power because the batts were isolated from the convertor. This was done on the circuit breaker block on the bulkhead behind the batts.

I moved some wiring on the block so that the disconnect switch wiring went directly from the batts to the block so everything was disconnected when the switch was thrown.

The wiring may have been done this way as a security measure, ensuring that the CO detector is always on and that the electric front slide doesn't open (I think it needs power to stay in the closed/open position from what I read in the manual).

I did the same years ago. When my battery switch is turned off, everything is off. My coach can sit for 2 months and still have battery power to bring th jacks up and open slides if needed.

Only took about an hour to rewire so that it is a true disconnect

If your inverter is anything like mine even with no a/c load if the inverter is not in stand by it will draw about 6 amps. If I put the inverter in standby mode the draw drops to about .5 amps. The only way to bring the draw to zero is to disconnect it from the batteries (i.e. with a cut off switch or something)

Sounds to me that your idea should work, I'd just make sure the amp rating on the cutoff switch is high enough for the load. If they used 1/0 cables (pretty pricey stuff) seems it either a very high load potential, a long run to the inverter or they ran out of smaller more reasonable size cable and just used what they had.

My bet is on the long run and that would mean heavier actual load near the source (i.e. at the cut off switch) since voltage drops over distance based on cable size even though the actual draw at the inverter may not be very significant.

BTW, the two pole connector block you mention that the 1/0 red cable goes to could that be a fuse? General rule of thumb is to fuse the connection on the positive side at the source. If so that can give you a clue what size the cut off switch needs to be.

Thanks for everyone's inputs. I even got a schematic out of redwood, although it is not exactly an "as built". I have market it up and attached the changes to the attached.
First, there is no 4/0 wiring. 4/0 is rated at 380 amps. The 1/0 wiring handles the inverter power and is rated at 170 amps. Plenty of juice for the fridge. The 6 gauge runs everything else inside the battery compartment although it looks like there are some distribution terminals that feed smaller gauge wiring for inside the rig.

My wiring change was very simple.
1. Disconnect the red 6 gauge from the battery to the cut off switch and replace it with a red 3' 1/0. I bought the 3 foot 1/0 wire on Amazon. It included a black wire too. The 6 ga. wire is of no further use.
2. Disconnect from the battery the red 1/0 wire that goes from the battery to the 2 pole terminal/ in line fuse. Leave the other end of the fuse alone. Connect this wire to the "common" side of the switch. Now we have switched 12V going to the inverter.
3. The 6 gauge red wire that used to connect to the "common" side of the switch now goes to the 2 pole terminal/fuse on the same post as the 1/0 red wire did in step 2.

You can leave all the black wires, both the 1/0 and the 6 gauge alone as they were.

Now all the power coming from the batteries, except that going to the generator, is cut off when you want it. 😛 😛 😛
The starter solenoid on the generator prevents it from drawing power until you want to start it.

Thanks, Ken. My switch is a blue sea systems 6006 and is rated at 300 amp continuous and 500 amp intermittant. You are also correct about the fuse.