My new batteries are not recharging on my motorhome while the engine is running the battery indicator shows over 12 volts while the key is in the on position, it's much higher in the off position, I can have it in the off position with the engine still running, because the shut off solenoid is bad and needs replacing. I do believe the house battery is charging while the engine is running, so I don't have a reason to suspect that it's the alternator, although that would be the first thing to consider. There was a red wire that ran from the isolator box to, I think the positive terminal of one of the batteries, I removed it when I replaced the battery cables, is it possible that is the reason the battery is not charging? Is anyone familiar with this cable and where it connects on the isolator?

Thanks