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Checking an alternator

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wedge40

03-15-2008 14:29:49




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I have a charging system problem and would like to know the steps to figure out what the culprit is. Tractor is a 1967, 4000, 3 cyl, gas.

The alternator light is on when the tractor is running.

I've check the wires to the alternator and they seem to have a good connection. I have not double checked the regulator yet.

How do I go about making sure the alternator is working?

The repair manual said to short the two terminals on the alternator together and the measure the voltage between this short and ground. What kind of voltage should I be looking for?

I will double check the regulator connection tomorrow.

As long as the battery is full, it starts right up.

TIA

Wedge

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GlenIdaho

03-16-2008 19:07:57




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 Re: Checking an alternator in reply to wedge40, 03-15-2008 14:29:49  
Wedge; Here's a test for your genny output.

1. Disconnect the armature (red) wire from the terminal on the generator. Connect a jumper wire across the armature and field terminals.

2. Connect the negatve lead of a 0-75 ammeter to the generator armature terminal.

3. Connect the other ammeter lead to the terminal of the armature wire.

4. Start the engine and gradually increase the engine speed to 1500 rpm while observing the ammeter. The generator output should reach or exceed 20 amperes.

NOTE: Stop the engine and disconnect the jumper wire from the field and armeture terminals as soon as the generator output is obtained to prevent overheating the generator.

5. If the generator output is below 20 amperes or is erratic, check the generator belt tension and adjust if necessary. Repeat the test. If adjusting the belt does not increase the generator output to 20 amperes, remove and repair or replace the generator.

If you need a test procedure for the VR post back. Hope this helps.

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L.K. MACK

03-16-2008 18:57:23




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 Re: Checking an alternator in reply to wedge40, 03-15-2008 14:29:49  
WEDGIE,
IF YOU HAVE A GENERATOR SEND ME OR OPEN YOUR E-MAIL AND I'LL SEND YOU A FLOW CHART.
MACK

THE FLOW CHART WILL NOT WORK IF YOU HAVE AN ALTENATOR



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wedge40

03-16-2008 17:41:43




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 Re: So does it have a Generator or an Alternator? in reply to wedge40, 03-15-2008 14:29:49  
Update.. I went outside and tinkered with the tractor today. Measured the voltage before starting and then again after starting at both idle and up to about 1600 rpms. All three voltage were about the same. Some where between 12.2 and 12.4 volts.
I will take the regulator off sometime this week and clean and emery cloth the contacts.

Thanks for all the advice.

Wedge



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wedge40

03-16-2008 04:21:10




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 Re: Checking an alternator in reply to wedge40, 03-15-2008 14:29:49  
Is this better?

I have a charging system problem and would like to know the steps to figure out what the culprit is. Tractor is a 1967, 4000, 3 cyl, gas.
The generator light is on when the tractor is running.
I've check the wires to the generator and they seem to have a good connection. I have not double checked the regulator yet.
How do I go about making sure the generator is working?
The repair manual said to short the two terminals on the generator together and the measure the voltage between this short and ground. What kind of voltage should I be looking for?
I will double check the regulator connection tomorrow.
As long as the battery is full, it starts right up.

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awhtx

03-16-2008 06:55:29




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 So does it have a Generator or an Alternator? in reply to wedge40, 03-16-2008 04:21:10  
It makes a big difference depending on Gen or Alt. If it still has the gen you can hook the wires to it so that it works like a motor. If it will run as a motor it will probably charge as a gen. Soundguy, who is one of the electrical experts on this site, can tell you how to hook it up as a motor.
The factory gen was made by Lucas (a British company) and there are many jokes concerning Lucas electrical products. When they fail most guys pull them off and replace them with an Alt. Fortunately I have a Starter/Generator/Alternator repair shop close by and the owner rebuilt the Lucas gen on my 5000 for me and he says they are a good unit. Most Starter/Alternator shops won't even look at a generator and they send you back out the door when they see you walk in with one in your hand. See if you can find a generator shop in your area.

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RodInNS

03-16-2008 09:29:38




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 Re: So does it have a Generator or an Alternator? in reply to awhtx, 03-16-2008 06:55:29  
Does the guy at your starter shop smoke dope?? The only thing good about Lucas generators is that they were very good for business for the starter shops. Those things were no end of misery here.

Assuming that is does still have the generator I'd probably open the reg up and clean the contacts in the reg with some emery cloth. After that, repolarize the generator. It's been so long now since I polarized one that I'm after forgetting how.... but look up one of Soundguy's many, many posts regarding this subject if he doesn't happen along soon with the answer. The info you need is there.

Beyond that, and assuming that all the wiring is good and it still won't work... I'd rip the whole bloody mess off and install a Delco 10si alternator. You can get them from this site with a tach drive installed. Put it on and the charging problem is gone, fini.

Rod

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awhtx

03-15-2008 17:37:12




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 Re: Checking an alternator in reply to wedge40, 03-15-2008 14:29:49  
That tractor had a generator, not an alternator on it from the factory. The regulator that goes with the generator has a tab on it that one of the wires to the warning light connects to. It is highly probable that whomever installed the alternator used a GM alternator with a built in regulator and the wire that turns the light off is not connected.



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GlenIdaho

03-15-2008 15:53:44




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 Re: Checking an alternator in reply to wedge40, 03-15-2008 14:29:49  
Wedge;

Place a volt meter on the battery with the engine not running. It should test 12.5 volts. Then start the tractor and put the volt meter back on the battery. It should now read about 14.5 volts. Rev the engine to about 2000 rpms and see if it reads the same. The alternator should maintain the 14.5 volts. If you have a Napa store nearby you can remove the alternator and they should be able to test it for you. Hope this helps.

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Dell (WA)

03-15-2008 15:23:47




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 Re: Checking an alternator in reply to wedge40, 03-15-2008 14:29:49  
Wedgie..... ..sounds like yer justta'bouta lett the SMOKE out'n yer alternator. You do know all electrical stuff runs on smoke don't you? Poof!!! the smoke out and it quits working everytime. (grin)

Hakeem's Razor sez, 95% of the time, RED alternator lite while running is BAD BRUSHES or broken fanbelt.

'course you could always do it the cowards way and take yer alternator in for a "free" checkout at enny autoparts store. Simple, eh?..... ..Dell

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