Jubilee is 24 years old and had her original 55 amp (?) alternator up until a recent trip from San Francisco Bay to the Sacramento Delta. With batteries down to half charge, the alternator was only putting out 10 amps at high RPM. When the engine was off, and all systems turned off, including the main and engine switches, there was a 2.1 amp draw. I discovered that the alternator was quite warm, even though the engine had been off for 12 hours. Bingo. The new alternator, an exact replacement, is now putting out 50 amps, while the old one did not put out more than 30 or so. The alternator shop guy explained how all of this to me, but it was mostly over my head. Mainly it had to do with blown diodes. He also discovered a place that had burned out, so the whole thing needed to be replaced. What got my attention is that with the blown diode, juice from the house batteries was getting to the alternator, (back through the positive charging wire) despite the main switches being off.

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