12 volt gauge on dash

[Yachts]

Was showing 13 volts running the other day.. Yesterday showed 11volts and battery acting like it was dead.. Even when you turn the coach off it shows 10-11 volts.. Bad alternator?

[77newell]

It could be a bad alternator or it could be a badly failed battery that soaks up all the alternator current. One way to tell is to use the converter to try charging the batteries and if they come up to voltage then it's very likely the alternator. If they don't come up to voltage then the batteries are gone and this can be confirmed with a battery tester.

[prairieschooner]

I agree and would start by looking at the batteries and checking the terminals (wait a while after charging) to be sure that they are tight and the batteries have reasonable voltage.
Since it does sound like you could have a charging problem the next step I would take is to get a volt meter. Write down the voltage before starting the diesel and then after while it is running. The voltage should be about 14 volts (roughly 13.8 to 14.2 depending on the type of batteries) when the engine is running. A reputable parts store or rebuild shop can help check the alternator and regulator for you after you pull it.
good luck

[Yachts]

Alternator is putting out.. When I plug in the batteries charge back up.. I think I had a bad belt.. Looked this morn and now I have no belt...gotta find one:(

[Chester B. Stone, Jr.]

Get two while you are at it.