the pointy end is the bow
Join Date: Aug 2006
Location: La Conner, Washington
Thanked 27 Times in 26 Posts
Rep Power: 11
IIRC, the voltage regulator controls the amount of current going to the spinning electro-magnet in the middle of the alternator. A stronger magnetic field induces more current to come out of the wire windings around the spinning protion. The electricity from the windings alternates back and forth from positive to negative as the north/south poles of the spinning electro-magnet spin pass them. The three wire windings pass through diodes. They act as an on/off switch and only allow the current to pass through only one way, either positive to negative, giving us D.C. current for our D.C. system.
If the brushes that make contact with the slip ring terminals to the electro-magnet are worn/dirty/weak springs, the regulator may be telling the electro magnet to produce a strong current, but it can't because it's not getting the voltage it needs. I recollect that you can check with this an ohm meter, but I don't remember how to do it off the top of my head. I had some alternator problems two years ago and found some detailed testing procedures online for checking the diodes. Without that, it would require splitting the case open and taking a look at the brushes. New brushes are typically .75 to .50 inches long. If they're getting down to .25 inches, I would suspect they're worn out.
1983 Fraser 41
La Conner, WA
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Boating for over 25 years, some of them successfully.