Even if the regulator is good, if the old contact point style, replace it with a new Bosch solid state version. My bus had one electrical problem after the other for years. I had replaced the generator several times and had put at least 4 regulators on it. Batteries would go bad about as fast as I could intall them. It would blow light bulbs constantly. A few times, for no know reason, smoke would start coming out of the instrument pannel. I put in a new solid state regulator and all of those electrical issues instantly went away.