chassis battery system problem

[togue]

I wanted to top off my four house batteries and two chassis batteries before I sell my 2019 Winnebago Forz 34T diesel. Disconnecting, cleaning, filling and reinstalling all the wires for the four house batteries went back together smoothly and all systems work properly. The two chassis batteries were easier to work on. But after removing two negative cables and the battery hold down bar I realized these were sealed batteries. I cleaned what I could and reconnected the two cables to the same negative pole. But when I plugged the shore cable back in and tried to turn on the chassis shutoff switch, it would not stay on. There is now no power to the ignition. I disconnected, cleaned and reconnected the two negative cables without getting power back. I'm guessing I must have shorted something. But where do I begin? Another issue is that when I downloaded the wiring diagram from Winnebago, it only shows one cable to the negative terminal. I have two -

[CA_Traveler]

Turn on the headlights and if they don't work that is another clue. Check the voltage should be 12V+. Wait at least 5 minutes and check again. This is a very basic test and at some point it would be a good idea to load test the batteries. Check other chassis battery items for operation like radio etc.

The shutoff should be mechanical, no fuse for it. Fuses or CBs however protect the wiring. From your description I would suspect the switch or the wiring. Flooded batterie create a lot of corrosion and I've seen cases where the cable no longer has a good connection to a terminal.

A bad ground wire is also suspect. This is why you need to measure from a good frame ground and not a negative wire. With the lights on you should measure 0V (or close) to the negative post and 12V to the positive post and 12V to the ignition switch etc. There should be a direct connection to the starter, no switch etc so you can also check there.

[togue]

I did not disconnect any positive cables. There is one negative cable from the other battery. The two cables both go through the cowling in back. I guess its possible the batteries are dead. I'll try to test the battery if I can do it with a multimeter? I don't know if I can find a fuse for the shutoff switch?

[CA_Traveler]

Use a voltmeter and measure the battery voltage from a good frame ground. If OK continue to the disconnect switch fuses etc.

Is the second negative cable going to the second battery? Did you disconnect any positive cables? Or enen a third negative cable?