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Tool Talk Discussion Forum

Alternator/Generator tester

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WilMan

08-28-2005 19:43:30




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Has anybody made their own generator/alternator bench tester? Also are their any good books on generator/alternator repair for someone who is interested in doing this themselves. Had to take the alternator in on my 12 volt converted tractor. An internal diode was bad and alternator wasn"t charging. Darn near $70 later, it was up and charging again. Looked fairly simple with what he did. Took apart and replaced the diodes etc. Don"t mind the parts cost, it is the labor charge for a 1/2 hour of work that gets me, exspecially if I can do it myself.

Thanks

Wil

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Jim Cox

08-29-2005 15:17:44




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 Re: Alternator/Generator tester in reply to WilMan, 08-28-2005 19:43:30  
I was an engineer at the New Holland Reman facility in Spfd MO for about five years. A good alternator tester should include a 5 hp motor, enough load for about 100 amps or so, and a ay to vary the load. A good machine was around $30,000 in the production world, you can get your stuff tested free at most NH dealers on a $6,000 machine, or go to Oreilly/Napa and use the $795 from junk-o-rama inc.

I don't know what kind of alt you had fixed, but a dependable guy in a Mom-and-Pop shop will be a great asset for years and years to come. Now that he knows you there will be some free advice just around the corner

Don't be afraid to pay for quality. It actually saves in the long run.

Jim Cox
SW Missouri

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Ken Crisman

08-29-2005 07:08:10




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 Re: Alternator/Generator tester in reply to WilMan, 08-28-2005 19:43:30  
$70.00 was not bad at all . You figure he had the equipment/knowledge to test & the parts to replace . Now you are up & running . Also consider the operating expenses he endures . What ever you do for a living , would you feel you're worth your paycheck ? Well that guy had to pay to get his shop set up , learn his trade , & buy parts & machines . A man is worth & entitled to his wages is my theory . I have finally realized that I can't save money by having my own shop for everything .Install your genny & be glad its fixed & working . Ken

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MarkB_MI

08-29-2005 03:52:31




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 Re: Alternator/Generator tester in reply to WilMan, 08-28-2005 19:43:30  
The only piece of test equipment you need for repairing alternators is a multimeter. You can use the meter to check out the diodes (shorted or open) and the rotor/stator windings (open or shorted to ground).

With newer alternators, you can't check the diodes or anything else without desoldering the connections between the stator and the diodes. But the older stuff is fairly easy to work on; you may need to desolder a few connections but they are usually easy enough to get to.

Repairing generators is a whole 'nother thing. You need some fairly specialized equipment (like a "growler").

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buickanddeere

08-28-2005 20:32:12




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 Re: Alternator/Generator tester in reply to WilMan, 08-28-2005 19:43:30  
You didn't pay very much for the labour. It's the building/business overhead, parts inventory and paying for the knowledge/experience. Somebody else could spend a day looking at that alternator and still not have it repaired.



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Hermit

08-28-2005 20:15:34




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 Re: Alternator/Generator tester in reply to WilMan, 08-28-2005 19:43:30  
Find some old Motors auto repair manuals at garage or estate sales. They have lots of good info on testing and repairing generators and alternators.



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tech4

08-28-2005 20:03:21




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 Re: Alternator/Generator tester in reply to WilMan, 08-28-2005 19:43:30  
Alternator and generators are pretty easy to repair and for home or farm use a volt ohm meter is about all the test equipment you need. The diodes can be checked and windings checked for continuity or shorts. A basic understanding of electricity is very helpful but some problems are mechanical like bearings. Many of the auto parts stores have an alternator/generator starter tester in the store that they will check for free. 90%of alternator problems are the diode bridge. click site below for some basics on alternators.

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Bryan In Iowa

08-29-2005 09:39:53




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 Re: Alternator/Generator tester in reply to tech4, 08-28-2005 20:03:21  
I always cringe when customer comes with the old " I took the battery cable off and it still runs , so alternators ok " story . Now most likely they have killed a diode in alt ,,and worst case, fired PCM .



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old

08-28-2005 20:51:42




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 Re: Alternator/Generator tester in reply to tech4, 08-28-2005 20:03:21  
I have to disagree with you just a little. Most alternators that I have had go belly up on me was caused by brushes going bad. So maybe its more like 50/50 as to brushes or diodes.



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Stickler

08-29-2005 05:56:25




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 Re: Alternator/Generator tester in reply to old, 08-28-2005 20:51:42  
I just had a ford alternator go belly up when the worn brushes wore into the slip rings. That's what ya get when ya don't bother to check them every few years. What should have been a 5 dollar fix wound up being a much bigger one.

Previous to that though, I've also seen the same, that it's usually diodes and the odd regulator that goes. I usually find short brushes and replace them then



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tech4

08-28-2005 20:08:39




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 link in reply to tech4, 08-28-2005 20:03:21  
Use this link and click the arrow on the right to move to the next pages



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WilMan

08-29-2005 16:39:01




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 Re: link in reply to tech4, 08-28-2005 20:08:39  
Thanks for the link Tech 4, just what I was looking at. I do have some old Plymouth manuals I will have to take a closer look at. I don"t begrude the guy what he makes, it just surprised me seeing it didn"t take that long and it looks so easy. He is a great guy and does give out some free advice but I am interested in doing this myself and learning how. What happens in 10 years or so when he retires and nobody takes over the store? I als want it so that the next time I take him something, it is because I really messed it up:))

Wil

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tech4

08-29-2005 18:45:52




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 Re: link in reply to WilMan, 08-29-2005 16:39:01  
Ok Wilman I knew that you just prefer to learn how to work on your own equipment. It is not just the labor cost but the time it takes to take a part to someone and sometimes wait a week for a repair and the satisfaction that you can fix your own tractor truck or car. Anybody that farms does not like to have to depend on someone repairing all their equipment. Keep on learning.



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