Mystery component on alternator

[jddh]

Hi friends, I’m trying to solve an alternator problem without ending my cruise & pointing my bow to the mechanic.

The question: Mitsubishi 50 amp alternator on a Westerbeke 21 engine. The alternator has a wire going from the B terminal to a gold component on the outside of the alt. What is this component? A schematic follows below.

Context: alternator is pushing 15V, sometimes greater, into the system. Seems to push more as batteries fill. Main battery wire on the alt gets hot. Not good. Not much to be seen externally on the rig that might be an issue, except that the wire going to the component I mention above is rather frayed. I’m trying to figure out if I should bother trying to reinforce this connection in the interest of solving my problem. I don’t imagine the external component in question is a voltage regulator, but if it were...now would be a good time to reinforce its connection!

(The alt is internally regulated; I don’t have an external reg installed)

Thanks for your thoughts.

[Reefmagnet]

That would be an rf suppression capacitor and would not be causing your issue. The voltage regulator is internal on that model alternator.

[Calif.Ted]

I believe Mr. Magnet is correct, BTW there are 3 Nantuckets on my dock, I tease them about being the ENTIRE West coast fleet of such vessels.

[Jammer]

Hello jddh


As posted upthread probably an rf filter. They were common during the LORAN era and still sometimes seen on boats that have HF transceivers. Rarely a source of trouble -- when they fail, they usually just stop working, or occasionally fail with an unremarkable explosion that mostly just makes a mess.


Re heat, it is important to be sure the B+ connection is clean, bright, and tight. It should be flexible so it is a mistake to use excessively oversize wire. If removing, cleaning, wirebrushing, and reinstalling the terminal (possibly with some contact grease) does not resolve matters you might want to replace the wire assembly (including terminals)

[Stewie12]

15 volts of not excessive.

[jddh]

Thanks very much @Reefmagnet et al — makes sense.

@Calif. Ted — it’s a Niagara 31 in fact! Sometimes not the easiest to find techs with Westerbeke experience. At least it uses Mistsu parts...

[Mike Banks]

That is a spark quench capacitor. Sometimes they short circuit and stop the alternator working properly if at all. Test it and if faulty replace it.