I've had to change out the volt meter on my 78 CJ5, it just went bad, but check the connectors at the alternator first. There should be two wires connected to a eye ring that is held onto the back of the alternator with a nut and a two blade wire connector on the side. If that is all ok check the volt meter connections and maybe put a test light on them. If the meter is bad just pop in another one.