Richard: I thought of that but then I wondered if it was possible to push the generator that high if it was overloaded.
Stan, you may be correct. Typical exciter maximum input voltage is 63 volts and the regulator typically operates in the 20+ range, so there is plenty of range but an overload may keep the voltage from rising that high.
In order to try and isolate a problem like this I usually used either a variable voltage DC supply to check the operation or several 6 volt lantern batteries connected in series to get up to the correct operating voltage.
It is really important that he disconnect any possible load before trying anything. It will be interesting to find out what the real problem is.