Yanmar 1GM Alternator

[Jim]

While cruising in my CD25D, my buddy accidentally turned of the master battery switch with the 1GM Yanmar running at ~1200rpm. He turned it back on instantly and the alternator seems to be still charging - the alternator charge light is off when the engine is running and the voltage gauge indicates charging as does a SG test. I know that the diodes on the alternator blow under these conditions and I wonder if there is any residual damage to the alterator that may lead to failure in the future. Someone told me that the diodes blow or don't. Any advice? And what are the consequences of turning off the instrument panel key with the engine running?
jim



james.jamieson@yale.edu

[Stephen]

While cruising in my CD25D, my buddy accidentally turned of the master battery switch with the 1GM Yanmar running at ~1200rpm. He turned it back on instantly and the alternator seems to be still

lead to failure in the future. Someone told me that the diodes blow or don't. Any advice? And what are the consequences of turning off the instrument panel key with the engine running?

The Hitachi alternator seems to be pretty sturdy. Mine has been seriously abused and still works. Part of the reason for this may be that the amperage is quite low (35 ahs in my case; 55 for newer ones).

I took it apart once and found not diodes, but an IC chip. I don't know how you diagnose it, but I think it probably either works or it doesn't.

As for the key turning, I wouldn't recommend it; I think it connects the alternator with the battery power system. If so, turning off the key while the engine is running would be the same as switching the A/B switch to off. I'm not certain, but think this is the case.

Nigel Calder in his book recommends the ZapStopper, essentially a special diode you connect between your alternator battery terminal and ground. In the event someone disconnects the A/B switch or otherwise disconnects the batteries, the ZapStopper is supposed to absorb the brunt of the impact. I have one and it may have saved my alternator; don't know.

Good luck,
Stephen



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