Over voltage.

HOLY CRAP!! Don't run it that way or at the least, unplug the VR

This sounds like an OPEN in the charge path/ circuit to the battery. Stock wiring? Bypassed ammeter?

The following SHOULD NOT apply or else the following may have caused the open: (or else battery would also be high, very high V)

Or a bad VR causing full charge OR shorted field terminal at the alternator

Bad wire terminal, bad bulkhead connector terminal(s) failed harness "welded splice"

Should not be bad terminals at the ammeter because you would have NO power (no lights no nothing)

Check the alternator.......remove both field wires, check both field terminals to ground. should be OPEN AKA infinity

If none of the above fixes it, CHECK that the VR IS GROUNDED, and if that is OK replace the VR