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Re: [T3] DBB alternator :Reply to jim..long


On Fri, 2005-03-25 at 10:45, Jim Adney wrote:



> It's also possible that a generator might arrive from a rebuilder in a reversed 
> polarity condition. I don't know if this ever happens, and I would consider it 
> a sign of shoddy or incomplete workmanship, but it's possible. If the generator 
> is tested by running it in it's correct direction and correct polarity, then it 
> is automatically correctly polarized in the course of the test.
> 
> Nevertheless, I don't even bring up repolarization in my generator FAQ, just 
> because I'm afraid that it would do more harm than good, and because it is 
> almost never necessary. In 35 years, I've seen exactly one generator that 
> needed to be repolarized, and that one had been run with the battery reversed. 
> The shade tree rebuilds that I do never need to be repolarized, but I never 
> remove the field pole pieces. I don't even know anyone who has the tools to do 
> that.
> 
The only VW generator I have ever had to "re-polarize" was one that was
rebuilt by a local shop. It would not charge when installed in the car.
Luckily it was a T-3, so no big deal taking it back off. I took it back
to the shop that did it, and they tested it, and said it was good. We
then discovered, that what they were doing was testing it on their test
machine in reverse rotation. They flipped the switch on their test tand,
and it didn't work. We polarised it and then it worked fine.
I do use the polarising technique to check a generator off the car. If
it runs like a motor, then it is probably good.

-- 
Russ Wolfe
'71 FB AT
'66 FB MT
'64 T34 (not running)
'65 T1 (not running)
'05 KIA Sorento SUV
russw@classicvw.org
http://www.classicvw.org

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