I was on the road to Asheville,NC last week and the voltage began to fall on the dash gauge and the battery icon showed up on the dash,I knew that I had a Guest charger hooked up to the coach batteries and I cranked up the generator and the voltage came up to 25.5-26.I only had 25 miles to go so I continued to my destination,the strange thing is that neither the alternator or the regulator have any thermal protection but when it all cooled down it began to work again.Today I left Asheville and in about 30 minutes the same failure happened again,the Guest charger could maintain 25+ volts for about 1 hour but then it fell to 24 volts so I stopped and hooked up a 30 amp charger that I carry with me and made it home.Prevost says that there is no thermal protection so I am trying to figure out if this is a alternator or regulator failure.Prevost has recommended a bus shop nearby and the shop foreman is convinced that the regulator is the problem.How can I verify that the alternator is not at fault and it really is the regulator.This coach has the 270 amp alternator and the Delco regulator.