Alternator condition : how to test or evaluate ?

[Vincent Gelinas]

I'm not sure I can pinpoint exactly what is wrong, but I used to have a 2000
Mercury Cougar V6 5spd.  Those cars are notorious for chewing alternators,
partly due to bad design of the big 3 (grounds), partly to a bad voltage
regulator.  I replaced the old one (massive bearing failure and was rattling
and blowing my alternator fuse) with a used one from a junkyard.  Godawful,
ethereal squeal coming from it the first time I used it in the engine, and
after a certain RPM (about 3.5k iirc) the alternator wouldn't put out a
charge.  Left me stranded in the middle of I-93 close to Lynn and Braintree.
 I would check your voltage and amperage, but beyond that, I'm not sure
what's wrong.  I always thought it might have been corroded brushes on the
commutator.  Though there may be corrosion on the stator.  Not sure.

Best of luck,

V

On Fri, Nov 26, 2010 at 3:53 PM, Louis-Alain Richard <laraa at sympatico.ca>wrote:

>
>
> -----Message d'origine-----
> De : Huw Powell [mailto:audi at humanspeakers.com]
>
>
> First, have you measured voltages?  Alt output terminal, battery terminal
> when charging and when off, etc.?
>
> ********* Well, not yet. Will do this week-end. I suppose I test it in
> different states : unloaded, full load, part load. Will write down the
> values for the list.
>
>
>
> Now, it is possible that your new VR brushes are "square" on the end, and
> until they wear a bit into a "round" shape to match the commutator, current
> capability may be a bit off, and it might even make noise.
>
> ********* Could be that indeed. The brushes were pre-formed obviously, and
> I
> did emery-cleaned the copper thingy (commentator?) before reassembly. I did
> notice the bearings were spinning very freely, like an old bearing with not
> much grease inside. Play was minimal.
>
>
>
> The "shrieking under load" isn't anything like belt squeal, is it?
>
> ******** Not a belt sound for sure. New belt, correctly tightened. The
> sound
> is more like finger nails on a black school board, if you know what I mean.
> (Now I'm sure a lot of you shivered reading that sentence :-0)
>
> Louis-Alain
>
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