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Old 26-05-2017, 08:16   #1
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Alternator Rotation, Or Other Problem?

A friend who swallowed the anchor gave me the spare high output alternator he had for his Perkins. He said it had never been used.

In an emergency I mounted it on my Yanmar, and while its being there allowed the engine to operate (the water pump being driven by the same belt), it did not produce current. So back went the old alternator (also high output externally regulated) after the bearings were replaced. This was a couple of years ago so my memory may be faulty, but I believe I took the new one to a shop, and they said there was nothing wrong with it.

I should have tried to resolve this at the time, but other things got in the way.

I've been told that an alternator is made to charge rotated in one direction only. I'd be surprised if my Yanmar rotates opposite his Perkins (mine is a Saildrive, but I don't think that matters) but is that a possibility?

Then I've read about different type alternators, P style or something, but I don't know what that means.

Any ideas out there?
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Old 26-05-2017, 08:30   #2
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Re: Alternator Rotation, Or Other Problem?

Electrically it does not matter, the fan is the thing. In a high output app, I would want it to blow/suck the right way.
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Old 26-05-2017, 08:40   #3
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Re: Alternator Rotation, Or Other Problem?

Do you have an external regulator?
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Old 26-05-2017, 08:58   #4
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Re: Alternator Rotation, Or Other Problem?

Electricity's fine, cooling is an issue, ideally look for a unidirectional fan.
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Old 26-05-2017, 10:28   #5
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Re: Alternator Rotation, Or Other Problem?

Yes, I have an external regulator, as did my friend.

So there must be an electrical difference between these alternators.

Fans:
I'm looking at my original Yanmar alt. and it has a unidirectional fan.

As far as the correct rotation for a directional fan, which is what's on the high output alts, I assume the fins need to be angled the direction to spin the air outwards, like a centrifugal water pump??
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Old 26-05-2017, 12:04   #6
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Re: Alternator Rotation, Or Other Problem?

I'm more familiar with the big Leece Nevilles, most are clockwise, but lots are bi-directional.

https://www.google.com/search?q=BI-D...gs_products%2F

And people do talk about retrofitting fans.

Take it to an alt shop?
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Old 27-05-2017, 13:30   #7
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Re: Alternator Rotation, Or Other Problem?

If it rotates, it should work: All alernator generate alternative current, that is transformed into direct current by a diode bridge. But the fan that cools it won't be efficient if turning 'backward'. Less air, risk of over heating of the beast, thus less
In my opinion you have a regulator problem, or no excitation of the field, or a bad connection somewhere.
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Old 27-05-2017, 14:02   #8
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Re: Alternator Rotation, Or Other Problem?

Alternators, externally regulated are connected differently inside and may not share the same regulator needs if made by 2 different companies. Fans in either direction are available on line.
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