Re: Maiden voyage of rebuilt SMB near catastrophe--need advi
Are the starter batteries charging from the alternator? If you have an isolator (~pre 2003? I can never remember) looks like a brick under the hood it should be putting out 12v when the alternator is.
If you have a separator (post 2003ish, and found in the cabin somewhere) it may not be closing. Regardless the line you found to the battery should have 12v unless the batteries are dead. If the line has 5v, the batteries have no more than that... and voltage that low can keep your separator from closing (joining drops the whole system voltage, the separator opens, etc)
With the alternator off the voltage on what you think is the line should match the house voltage, eg. 5.25 both places or whatever. You can check the house voltage in the power outlets in the walls.
Without more info it's hard to guess what is wrong.