Drain on Genset Battery

[xz3kg7]

I'm leaving tomorrow for a 3500 mile roundtrip vacation... and of course I just
discover a problem I haven't had.

I have new batteries, all the way around. 6 new coach and 1 new genset batter
(genset is 8k, kohler, I think). I have never had an issue with the genset
battery draining, but I do now. I charged it for 12 hours yesterday, and this
morning, about 12 hours after charger cut off, it only had 10.3 amps (volt
meter), apparently not enough to turn the genset.

This battery is 3 days old, I replaced the last one because I thought it was
probably bad.

Only other clue I have is that the genset DC volt meter on overhead console is
not reading. (needle lays all the way left, less than 10vdc). I have not noticed
the meter not working before, so if it is not tied to the issue, it is a new
problem.

Of course, what I'm worried about is draining coach batteries overnight and then
not being able to start genset to get coach started. I'm contemplating bringing
along an extra car battery and putting it in a compartment to jump the genset...
but what a hassle.

Does anyone know where the isolator is on an 87FC35, and how to test/fix it...
or do a temporary fix? I'm halfway decent with a voltmeter.

Thanks!
Alan
87fc35

PS. I'm leaving Dallas and going to the North Rim of the Grand Canyon, Zion
National Park, ...other places north through Utah and Idaho. Then Yellowstone,
Mount Rushmore and South Dakota Bad Lands. I'm really looking forward to getting
out of this heat.