I assume you are discussing the charging of your chassis starting batteries.
Start the engine, rev it to 1000 rpm and take a reading with your voltmeter at the battery terminal. It should be about 13.6 dcv as the alternator is replacing the charge used in starting the engine.
If not, then you have a problem between the battery and the alternator.
Loose connections or dirty connections could be the problem and the cheapest to fix.
My rig has a battery isolator that splits the alternator charge between the chassis battery and the house battery.
Otherwise the starter and the alternator are the only other connections I am aware of.
