Alternator help

Zachary Hoyt · Apr 13, 2010

I got the H to run again after it quit on me and it was doing okay for a while till the alternator quit. I believe it is a Delco, it is certainly a 3-wire. When I got the tractor the seller told me to pull out a knob on a box on the lightbar to charge the battery and push it in when the tractor was not running to keep from draining. One day I pulled the knob out and the ammeter didn't show charge, but all the time when the engine is running the needle waves back and forth. I tried jumping the switch mentioned above but that didn't help. How can I test a 12v alternator, or what else should I be looking at? Thanks for any help.
Zach

Jeff Z. · Apr 13, 2010

Pop it off and run over to Burlington and have Auto-Zone run a free test on it.

Bob · Apr 13, 2010

Check the output voltage of the alternator.

Check the voltages at the #1 and #2 terminals and post back. #1 should have battery voltage when the "excite switch" is pulled yo "ON". #2 should have batery voltage at all times.

old · Apr 13, 2010

Easy way to check things if you have a meter is to check battery volts when not running should be around 12.5 volts and then with it running and running it should be around13-14 if the alternator is working like it should be

Zachary Hoyt · Apr 13, 2010

Bob, thank you very much. I am not sure which terminals are which, but with the switch pulled all three terminals on the alternator read in the 11-12 volt range when I grounded the other tip on the multimeter. The battery also read 11.96-12.02 volts. I am thinking this means the alternator is dead, but I'm not sure. I took a couple of pictures. If I need a new one do you happen to know a part number for one that would fit? Thanks again.
Zach

Zachary Hoyt · Apr 13, 2010

I took a couple of pictures. It looks pretty old to me, so maybe it got worn out.
Zach

Bob · Apr 13, 2010

If you had the engine running when you took those voltage readings the alternator isn't working.

<img src = "http://i167.photobucket.com/albums/u125/27Grainfield/424IH/Alternator%20Stuff/IHdelco.jpg">

I numbered the terminals for you... #1 gets voltage only when the switch is "ON", and should have an "idiot lamp", diode or resistor in-line to prevent the backfeeding of current OUT that terminal.

#2 is the "voltage sense" terminal and on automotive apps it's connected to a point near the (+) battery cable to sense voltage as close to the battery as possible. For theses simple tractor conversions it's typically just jumpered over to the alternator's large output stud.

<img src = "http://i167.photobucket.com/albums/u125/27Grainfield/424IH/Alternator%20Stuff/AlternatorHarnesssd.jpg">

<img src = "http://i167.photobucket.com/albums/u125/27Grainfield/424IH/Alternator%20Stuff/AlternatorHarness31.jpg">

It's a 10SI Delco. Simply ask the autoparts folks for an alternator for a 1975 Chevy pickup with 350 engine, NO air conditioning (unless you want a HIGH output unit).

Zachary Hoyt · Apr 13, 2010

Thank you very much. I looked the 10SI up on the NAPA website and it says they have it. I'll call them tomorrow during business hours and ask them to get one in for me. That explanation of what goes where is very helpful. Thanks again.
Zach

Nates90 · Apr 14, 2010

You can also do a quick test while the engine is running, take a screw driver and see if the metal cap on the end of the alternator is magnetized.

Alternator help

Zachary Hoyt

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Jeff Z.

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Bob

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old

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Zachary Hoyt

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Zachary Hoyt

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Bob

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Zachary Hoyt

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Nates90

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