1999 Chieftain 35U 12 volt issues

[Morich]

I'm in a bit of rush right now and not able to read it all again to refresh, but are you sure you have good coach batteries?
When things won't run at first try but then run when the engine is running, it may be as simple as the coach batteries are not getting or not holding a charge.
Maybe they can't handle the load when on their own, but when the engine is running the alternator is providing the power and doing a "quick" charge of the coach if they are dead?That would let all the coach items work but only as long as the alternator is doing the real work of providing power.

What can get confusing is that they may also appear to work when we stop the engine but then die shortly after we shut that down as they did not actually have a deep charge to last hours, just a small surface charge.

One point on battery charging is that it takes HOURS to really get it done. One way to know you are not getting a true full charge if you read the voltage too soon is that you may get a reading above 12.8 volts.
That is always a bogus reading because the best a lead acid battery will hold is near 12.8!

Maybe time to review if they are actually good batteries and really getting the full deep down charging over 6-8 that they need?

[treimche]

I’m definitely not sure they batteries are good. They’re only 3 years old but they were low on water and had very dirty terminals. I’ve had my battery maintainer on them for the past week or so in order to help charge. My new converter/charger just showed up today so I’ll be installing that tonight and if the batteries don’t charge from this one, then I will replace them.