Re: Shaft generator doesn’t load

Roland Mueller


The 24V alternator failed because the wire to enable charging was loose. After fixing this wire properly, the 24V alternator worked fine. And helped us to complete our journey from Leros/Greece to Genua/Italy.

The voltage of the 24V batteries is 25.8V, hence fully charged. There should be sufficient voltage to generate field current.
The voltage on the field wire to the alternator (the small wire) is measured 27.6V (currently at shore power).

What could be defective at the shaft alternator, that worked perfectly fine before our 24v supply breakdown? I can't believe it's a mechanical issue. We've check all wirer connected to the shaft alternator, just to make sure we are not fooled again by a loose wire.


From: <> on behalf of Bill Kinney <cruisingconsulting@...>
Sent: Sunday, June 19, 2022 4:04 PM
To: <>
Subject: Re: [AmelYachtOwners] Shaft generator doesn’t load

What is the current voltage of the batteries?  If it is VERY, VERY low then there might not be enough voltage to generate the required field current.  I think this is unlikely, but possible.

Other than that, I can think of nothing that could be related between the a deep discharge of the 24V batter bank and the failure of the shaft alternator.  The first place I would check would be for voltage on the field wire to the alternator (the small wire).  If that is not +24V to negative, then that's the issue.  Find out where the break in the circuit is.

If there IS field current, then... it's time to dive into diagnoses of the alternator itself.

What happened to the main engine 24V alternator?  Why did that fail?

Bill Kinney
SM160, Harmonie
Le Marin, Martinique.

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