Vanner Issue? - unequal charge of starter batt's

[JT4SC]

Hey everyone,

Got an issue - I took the Moose (1993 MCI 102C3) out for a family road trip, everything ran great except one of the starter batteries (let's call it Battery A) started boiling/offgassing like crazy on the last leg of our trip.  When I got home I replaced the batt's and pulled out my voltmeter to check the charge when the bus was on.  Battery A (hooked up to the 24V input) was reading 15.11 volts, and battery B read 12.34.  The batteries are in all ways equal - there should not have been any compensation needed for a weaker battery.

I am attaching to this post a wiring diagram I drew up of my battery compartment.  Maybe the wiring is not correct?  It's been as shown in the diagram the entire time I have owned the coach, so I don't believe that's the case.  My limited bus/electrical knowledge leads me to believe this is a Vanner issue, but would appreciate any and all feedback/advise.

I also attached a picture of the busbar (shown in grey on the diagram), as well as the "CDLA - 10" (which is the only thing I can make out on it), which is shown in red.

Thanks so much!!
Jim

[buswarrior]

Test the Vanner.

There's a procedure to do so on MCI website.

Pretty simple, it either works or it doesn't.

Happy coaching!
Buswarrior

[chessie4905]

Load test the existing battery or use a hydrometer to check specific gravity of cells. A good battery dealer has the new electronic tester.

[JT4SC]

Test the Vanner.

There's a procedure to do so on MCI website.

Pretty simple, it either works or it doesn't.

Happy coaching!
Buswarrior

Thanks guys, I will hunt down the Vanner test on the MCI website and report back my findings.  As for the batteries themselves, I have a load tester and both of them are as you would expect from new batt's, nice and strong.