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opinions needed: should i rebuild this alternator, or replace it?
Hi,
I just pulled my alternator due to a failed bearing retainer, aka tolerance ring. the fan was wobbling and noisy. now that I've got everything apart, I'm wondering if I should repair this unit or replace it. there appears to be some evidence of damage on the stator ring, but I'm no expert. As far as I know it is still functional (except for the bearings). I'd appreciate any opinions. thanks! Here is where the stator looks possibly damaged. One half of the ring looks polished and/or scraped. here's one edge of the area: http://i326.photobucket.com/albums/k...psfbf6c359.jpg here's the other side of the area: http://i326.photobucket.com/albums/k...psf9dc6cd9.jpg see the metal shavings magnetically attached and protruding from the rotor? is this expected??? is this metal from the stator ring? http://i326.photobucket.com/albums/k...ps844a5afe.jpg brushes seem ok, possibly ~50% remaining (?): http://i326.photobucket.com/albums/k...ps9603a81f.jpg Minor grooves on the contact rings: http://i326.photobucket.com/albums/k...ps126f197b.jpg thanks in advance for any thoughts or opinions! Brian |
Junk it, get one with a more reliable solid state internal VR.
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+ 1, tried that old fix it myself save some money route, 12 months later pull it out again,(cheap and nasty regulator,fried battery and now acid leak through trunk of car )by the looks of your alternator it`s time to replace and forget, I bought a recon one 3 years ago, have not looked back, you don`t want to be pulling that thing out again in the near future. Just my own experience with type of alternator and it`s location. Cheers
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The alternator stator has 'shorted' windings the result of the rotor 'dragging'.
It needs the stator rewound. That alternator (SEV Marchal) was the most reliable alternator with the external regulator used in pre-1990 911s. |
The rubbing between the two parts looks to me to be cosmetic in the pictures. as long as there is no damage to the stator windings or the Rotor you should be able to replace the bad bearing retainer. The cost for a replacement alternator will run in the high $300 range. If you are handy then replacing the bearings and brushes would be a whole lot cheaper. It has been a while but the last time my alternator had an issue with charging the car had about 90K on the odometer. The dreaded red light came on low and stayed on all the time the car was running. It turned out to be one of the exciter diodes that provides the feedback to the voltage regulator had died. These are not the power rectifiers. In my own situation I enjoy the challenge of fixing things and have no problem with tearing it apart to find a problem. Worst case for me is learning that there are something's I just can't do. In this case, I replaced all three exciter diodes with 1N4000 diodes from Radio Shack. While I was in there I replaced the bearings and brushes. I believe I did not spend more that $50~75 bucks to do the job. Granted, this level of repair is not for everyone and you will never know how long it will last. If or when it does fail again, I will tear it apart again to see if I can still fix it. If I can't then I learned something and my out of pocket will now be $400 Plus. Yes, I did spend my personal time, but for me it is a pleasure to do and not a job so my cost for labor is zero.
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Take it to any good electric motor repair shop and ask for an assessment.
They can test the windings. May just need cleaning and new bearings. |
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if the stator is bad. When the rotor 'drags' on the stator, it causes the stator laments to move and touch the windings causing a shorted winding to stator. "It turned out to be one of the exciter diodes that provides the feedback to the voltage regulator had died." Rarely a problem. |
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"Shorted" laminations result in eddy current flow that disrupt the magnetic field pattern. |
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Do the hundred more and get a new one, Verlo, in the box, no core. instead of one that is just fixed the problem it had.
Bruce |
thanks everyone for the advice. I decided to take it to a local shop. A quick test showed the stator is not shorted and i was advised that it is in relatively good shape. Hopefully I'll have it back in a couple days.
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the long term reliability is definitely reduced. |
The rebuilder tested the stator.
I'm not too worried about long term at this point. Now that I've gotten it out once, I can pull it again if necessary. The current problem (sorry for the pun) seemed to be the bearings alone and not related to electrical performance. Hopefully this is the case. We'll see what the rebuilder says about the unit. |
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http://physics.stackexchange.com/questions/93757/reducing-eddy-current-losses |
Good for you for keeping the original and the external VR. In my experience the internal VR is NOT more reliable-- being a couple inches above a 200F motor for its entire life is no way to treat an electrical component-- a solid state one over on the electrical console is further from the heat and vibration.
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Solid state automotive electronics designs are unbelievably reliable these days. |
If you replace measure thickness if the alternator as the fan shrouds have different depths verb though they maybe 5r.
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The problem will be overheating in long duration high output conditions, leading to eventual failure. |
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