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post #11 of Old 02-03-2014
Maine Sail
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Re: Cooling problem solved now what's wrong with my tach?

Originally Posted by MarkSF View Post
My boat came with a blown alternator, and then I blew the diodes on the replacement by turning off at the key before stopping the engine. In both cases, the tachometer would not work. As Faster says, you really need to check that you have a healthy charging voltage - 14V or more.

If not, either the alternator is faulty, or it is not getting the excite voltage via the ignition switch.


I would love to know exactly how that alternator was wired so that turning off the key disconnected it from the load? Turning off the key has zero effect on most alternators. The only time it would, could be if a PO improperly wired something... Most factory alts are either key on excite or self sensed. With key on excite turning the ignition key off just turns off the regulator and the alt shuts down. With self sense excite it keeps on working even with the key off and unless the key also turned off the battery switch or other funky home brew configuration then the alts keeps running.

-Maine Sail / CS-36T

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