Originally Posted by 73shark
Yes the alternator should charge the coach batteries when the engine is running. As to the other problems I don't have a clue. It seems like there are a bunch of electrical problems with these various Interstates. I know I've had my share of electrical problems.
I ran into this early in my Interstate ownership. If the house batteries are above 10.5 volts or so (don't know the exact figure) the alternator will
charge them. But if the house batteries drop too low, there's apparently some relay that disconnects the house and chassis systems, and the alternator will no longer charge the house batteries. I think it's some kind of safety feature to make sure that a problem on the house side doesn't affect the chassis systems.
My house batteries didn't get down to 5.4 volts, but getting down to 8.5v or so was bad enough. I ended up recharging my house batteries on a bench, using a good multi-stage charger over the course of about two days each.
Solar won't work when the batteries get too low, either. The charge controller doesn't run off the panel, it runs off the batteries. So if the batteries get too low, the charge controller quits working and the solar panel can't charge the batteries.
Most of my electrical problems have NOT needed repairs, just a more complete understanding of what systems are draining the batteries while the unit is stored, to make sure those systems are shut off.