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alternator wiring

Dan Morehouse

Member III
I was trolling thru an alternator thread from a couple years ago and found a post by Maine Sail which showed the back of a 90 amp Leece/Neville alternator. (I'd link to it, but for some reason I can't copy or paste from the website field). I expected to see a wire capable of carrying 90 amps of current, but the biggest wire was #12 guage. And, the label on the alternator said "Amps-5". Someone on this site knows the reason for this apparent contradiction, and I am so curious that I'm ready to display my ignorance to find out. If an alternator is capable of producing 90 amps of charging current, why is there a conspicuous absence of a wire sized to carry that current?

Dan Morehouse
1981 E-38 "Next Exit"
 

tenders

Innocent Bystander
That's this thread:
http://ericsonyachts.org/infoexchange/showthread.php?t=7251

His (superb-as-usual) pictures show only the alternator and the wiring that's part of the alternator and regulator.

The big wire that attaches from the output and goes to the batteries isn't shown. But it would have an eye crimped onto it and would be held down with one of the large nuts on the output studs--I think the one being pointed to by "pos" on the sticker.

The ground would be attached to the "neg" stud with a similarly sized wire. Or, the alternator might be naturally grounded to the engine through the attachment bolts.

--EDIT: see the last photo in Mainesail's post where "12 Volt Out" and "Ground" are clearly labeled. The wires you'd use aren't attached. The wires you SEE are sensing wires so the regulator does its job, they don't carry the output.
 
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Dan Morehouse

Member III
Right...nice catch. But the label "Amps-5" is still curious.

I need to pull my alternator off and look at it again. I'm pretty sure it is also a Leece-Neville, probably the minimal amp charging capacity, and pretty sure with the stock mounted regulator like shown on Maine Sail's post. And I'm dead certain that IT has no wire larger than #12 attached to it anywhere, and that the wires run from there back to the ignition control panel in the cockpit. Even if it's only rated at 55 amps, that seems way too far a run for a wire of that size to deliver that charging current to the batteries. There's a terminal flopping around on the back of my alternator, but it's still working for the moment...however, that excellent post has whetted my appetite to replace it, not least because of the huge cost savings over a Balmar, etc. of the same capacity. I just want to make sure I plan the cables appropriately.

Dan Morehouse
1981 E-38 "Next Exit"
 

Lawrence B. Lee

Member III
Big Wire

Dan,
I installed the aforesaid 90 amp Leece/Neville alternator on my 32-200's Univ. 25XP a couple of years ago. I use a Balmar ARS 5 regulator. The big wire coming off my positive terminal is a #8 and it goes to the starter motor and then on to the battery bank. There is an in-line fuse between the starter and the bank. I do not recall the fuse size but it isn't small.

Larry Lee
Annabel Lee E 32-200
Savannah, GA.
 
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