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#1530464 - 07/13/09 10:28 AM Re: replacing bearings in alternator [Re: pzev]
bdcardinal Online   content


Registered: 06/03/05
Posts: 8645
Loc: Santa Barbara, CA
 Originally Posted By: pzev
Me thinks all my high RPM driving and constant shock loads did a number on the factory unit.


on the police interceptor crown vics ford has a one way clutch on the alternator pulley for just that reason.
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#1530654 - 07/13/09 01:52 PM Re: replacing bearings in alternator [Re: bdcardinal]
brianl703 Offline


Registered: 05/07/04
Posts: 10488
Loc: Manassas, VA
 Originally Posted By: bdcardinal

on the police interceptor crown vics ford has a one way clutch on the alternator pulley for just that reason.


Saab has the same setup on the 93. They call it an IDP, isolator decoupler pulley.
link

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#1530665 - 07/13/09 02:10 PM Re: replacing bearings in alternator [Re: brianl703]
nthach Offline


Registered: 01/02/04
Posts: 2000
Loc: California
I got bearings at Grainger - they stock NTN or Dayton(house brand).

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#1531356 - 07/14/09 12:33 AM Re: replacing bearings in alternator [Re: nthach]
severach Offline


Registered: 02/04/08
Posts: 617
Loc: MI or LA
My alternators use 6203, 6303, and 6204 bearings which are easy to find. Unfortunately the only ones I could find cheap locally were low quality mower bearings which can't take the heat and RPM of an alternator so I bought from eBay. RBI/RBTech seem to have the specs at a good price.

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#1531426 - 07/14/09 03:40 AM Re: replacing bearings in alternator [Re: severach]
nthach Offline


Registered: 01/02/04
Posts: 2000
Loc: California
Grainger was able to get me 6203 and 6303, 6L025 and 6L052 is their stock number. Both are NTN, double-sealed and filled with Chevron or Shell urea-base grease.

My idler pulley and my alt are riding on Grainger-sourced bearings, I was shocked that Delco-Remy who remaned my Denso alt used cheap Chinese bearings in it - my brushes were worn caused the idiot light to turn on.


Edited by nthach (07/14/09 03:42 AM)

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#1531437 - 07/14/09 05:10 AM Re: replacing bearings in alternator [Re: nthach]
Jim Spahr Offline


Registered: 07/02/03
Posts: 996
Loc: Lexington, SC
I thought the total alternator rebuild would be the bearings, the brushes, the regulator, and the rectifier. It seeems you are focusing on the bearings with only a passing mention of the brushes or the regulator. No one has even mentioned the rectifier.
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#1531719 - 07/14/09 11:31 AM Re: replacing bearings in alternator [Re: pzev]
mechtech2 Offline


Registered: 09/05/06
Posts: 19479
Loc: Chicago Area
For your own car, you can certainly grease the bearings.
Don't pack them full - 1/2 to 3/4 full.
Pop off the end caps to clean them and regrease them.
ARe they dry and worn out? Then get new ones.
But if you are in there and are replacing other things, sure you can grease them again.

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#1531746 - 07/14/09 12:39 PM Re: replacing bearings in alternator [Re: mechtech2]
Donald Online   content


Registered: 03/21/04
Posts: 16641
Loc: Upstate NY
In some cheap rebuilds they unsolder and solder back in broken diodes. The local rebuild shop around here replaces the entire diode bridge.
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#1531799 - 07/14/09 01:48 PM Re: replacing bearings in alternator [Re: Jim Spahr]
nthach Offline


Registered: 01/02/04
Posts: 2000
Loc: California
 Originally Posted By: Jim Spahr
I thought the total alternator rebuild would be the bearings, the brushes, the regulator, and the rectifier. It seeems you are focusing on the bearings with only a passing mention of the brushes or the regulator. No one has even mentioned the rectifier.

I pulled a rectifier trio off a wrecked car like mine, but it had a BRAND NEW Denso reman, so I seized the opportunity and smuggled the rectifier and voltage regulator. I bought the aftermarket WAI ones, the rectifier failed a Kragen bench test since it had 8 diodes, 2 more than OEM.

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#1532385 - 07/15/09 12:28 AM Re: replacing bearings in alternator [Re: Jim Spahr]
severach Offline


Registered: 02/04/08
Posts: 617
Loc: MI or LA
 Originally Posted By: Jim Spahr
I thought the total alternator rebuild would be the bearings, the brushes, the regulator, and the rectifier.

I can do worse than that. Of the two bearings I may only replace the front if the rear looks good and is too hard to get. The rear bearing usually lasts longer than the alternator because it has no belt load. That's why GM uses a big bearing in the front and can get away with a tiny cup of needle bearings in the rear. Many companies use smaller or lower quality bearings in the rear.

The brushes I just estimate the percent left and compare it to how long I think I'll keep the car. The cheaper they are the more I am willing to discard. Replacing early prevents damage to the brush commutators.

Bearings and brushes wear out all the time which keeps them cheap. The other parts including the regulator and rectifiers only fail catastrophically. Most never wear out which makes replacements expensive. I get them from a junk yard alternator or just let the rebuilders deal with it.

You might rebuild the whole thing for the education but it would cost more than a rebuild which is part of why those kits aren't around any more. When you learn what fails and what doesn't you can slash costs to a fraction of the rebuild price and have the same failure rate as a rebuild. A recent alternator rebuild on a 1998 GM full size was $10 for two bearings and $10 for the brush assembly. This regulator variant never burns out. That's $20 for another 150,000 miles. It was so cheap that I did the 1997 GM full size even though the brushes had some 40% life left. Getting my last $4 from the brushes just isn't worth it.

On my 1994 GM small car I destroyed a 3 year old C series alternator case front on a botched reinstall. The C rears are interchangeable and I have plenty but I had no matching fronts. After giving myself a swift kick for flubbing the Quad 4 Chinese puzzle bracket I assembled something resembling an alternator from the worst available parts and marched right down to Autozone and handed over the cash.

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