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Discussion Forum

#$%^! Thing Won't charge...

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09-09-2001 04:14:53

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Just brought home a middle 70's crawler. I can get around good with mechanicals but the charging system always escapes me. I can't begin to guess how many times for how many Tractors I bought an alternator for a 79 Chevy Caprice with air conditioning ( gets you a 50 amp alternator ) from Auto Zone for $20 exchange ( Any GM alternator ) if you don't want the life time warrantee. I then send to JC Whitney's for their 1 wire alternator conversion kit which literally lets you run one wire from the alternator to the battery ( through an amp gauge if ya want ) & your done & charging.. All the wiring on this crawler is intact/good. Has a seperate voltage regulator. I have a volt/ohm meter. Before I rip out all the old wiring & send away to JC Whitney for another conversion kit, can any one tell me how I might test the existing alternator/voltage regulator before I rip it all out? If I was sure which was the problem I would try to repair/keep the existing...

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09-09-2001 20:12:41

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 Re: #$%^! Thing Won't charge... in reply to Bill, 09-09-2001 04:14:53  
Bill, you didn't mention what kind of alt. you have on your crawler or what make of crawler for that matter? fill in the gaps and I'll send you the diagram you need and procedures to test it. Now I won't buy most electrical parts from Auto Zone. (I was a warranty center for them locally and dropped them due to quality problems) But they have one thing going for them, they test alt. for free so if yours can be removed easilly then by all means let them test it.

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09-10-2001 06:03:33

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 Re: Re: #$%^! Thing Won't charge... in reply to Darren, 09-09-2001 20:12:41  
So far I think yours is the best suggestion. Will couple it with another.. Current plan: Take out the alternator-3 wire ( Allis Chalmers HD4/652 same thing.Wiring diagram would help.THANKS!!!12 volt system already.) Spray contact cleaner through all the brush areas of the alternator for dirt build up, blow it out & then to Auto Zone for the test. With a little help from several viewpoints a plan comes together. THANKS!!1

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09-09-2001 20:07:22

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 Re: #$%^! Thing Won't charge... in reply to Bill, 09-09-2001 04:14:53  
If it has an alternator already, your best bet is to just swap it. Don't send to Whitney for a kit, If you can hook up one wire, you can hook up two and just add a light to the dash. The light needs to draw enough current to 'charge' the alternator circuit and will get 12V from your ignition switch when you turn it on. Too bright of a bulb (not enough resistance), and an ignition engine won't shut off when the key is turned off. Don't buy a new alternator, just go to your local car yard and get a used one. Most will be warranted for 30 days, and you can ask them for a double pulley if you choose. A truck alt with air will probably get you 70 amps, too.

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09-09-2001 19:41:21

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 Re: #$%^! Thing Won't charge... in reply to Bill, 09-09-2001 04:14:53  
lot of earthmoving eq gets so much dust in around brushes that they don't make contact with sliprings/communtator bars. don't quess your problem is that simple.

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Greg D.

09-09-2001 11:28:05

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 Re: #$%^! Thing Won't charge... in reply to Bill, 09-09-2001 04:14:53  
No offense to Mark, but I`ve got better things to do wth my time than screw around with a few dollars worth of alterator. It either works or it gets exchanged for one that does!!!!! If you have three wire system with an external regulator, unhook the regultor and plug into the connectors on back of the alternator to do the same as the regulator. If it charges, you know the regulator is the problem. I can`t even find a schematic of an alternator with external regulator in my Delco book so I can`t help you on connections. A generator is even easier to figure out, ground the fiel connector on the generator. If it charges the regulator is the problem, if not the generator is the culprit. I just don`t think it`s worth screwing around with a 12 volt alternator when the cost isn`t that high to sart with.

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09-10-2001 00:12:34

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 Re: Re: #$%^! Thing Won't charge... in reply to Greg D., 09-09-2001 11:28:05  
Grounding the field on some model generators will work but there were two types. One, I can't remember which way it was grounds the field to control the generator charge, and the other type puts 12+ to the field. Grounding this type will do nothing and you will think the generator is bad when it may still be the regulator. Also, you can buy one wire re-built GM alternators from any good auto parts store. They have an internal regulator and only need one wire going to the positive lead of the battery. Also if you have an old tractor with a positive ground system, you can reverse the polarity of the battery and add an alternator (negative ground system now). You see the only part that cares about polarity of the electrical system is the charging system. Starter will work just as good (same direction) and ignition system will also work. I did this conversion on an old John Deere Model 60 that I am restoring. I want to go in Christmas parades with lots of lights and want a good charging system. Dust can be a problem with automotive alternators but it may not be a problem depending on where it is, amount of dust, etc, etc. Hope this helps...
Oh, disclaimer, on computer cars or anything with a computer you can't change the polarity but who would want to as they are already negative ground.


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09-09-2001 08:28:19

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 Re: #$%^! Thing Won't charge... in reply to Bill, 09-09-2001 04:14:53  
Alternators without internal regulators almost always have some mechanism so that you can bypass the regulator and see if the alternator is OK. Some have a hole in the
back that you can stick a screwdriver into and short a tab to ground. If the voltage comes up, then the regulator is probably bad.

My experience has been that it's best to just pull the alternator off and disassemble it. Reason is that an alternator with blown diodes can cause the regulator to fail, so you'll
just keep replacing regulators when it's really the alternator that's bad.

Once you take the alternator apart, there are a few simple checks that you can make with your ohmmeter that will nail the problem 99 percent of the time.

First, inspect the brushes to make certain that they aren't simply worn out and that the leads aren't broken. Note that a burned up brush lead can be symptomatic of other
problems, so don't stop there.

Take your ohmeter and check continuity through the rotor (slip ring to slip ring). Then check between a slip ring and the rotor shaft to make certain it isn't shorted.

After the brushes, the diodes are the most likely culprit. Your alternator has six diodes; each one is an electrical check valve that only allows current to flow in one direction.
The diodes need to have one lead free when you test them; on some alternators it's just a matter of taking some nuts loose, while others require you to desolder the diodes
from the stator. Test each diode in both directions, it should show continuity one way and open the other. If you have a digital meter, be sure and use the scale marked with a
diode symbol, the other scales may give false open indications.

Some Delco alternators also have a "triple diode", which is just a small device with four leads. (I think it was used to run the alternator light.) Test it with your ohmmeter; treat it like three diodes with one lead tied together.

The stator seldom fails, but each of the three stator legs should show continuity to each other, and the stator shouldn't be shorted to ground. You probably can't test it without
disconnecting the diode pack.

That's pretty much it. You should be able to get parts at any place that rebuilds alternators.

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Audra Krzeminski

01-29-2003 11:56:21

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 Re: Re: #$%^! Thing Won't charge... in reply to MarkB, 09-09-2001 08:28:19  
I was wondering if you could get me a step by step guide on how to take apart an alternator? If so thanks. Audra

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