Delco 10SI, and other common alternators used used as upgrades in vehicles, rely on magnetism in the spinning rotor. The magnetism is created by electricity that is turned on by the internal voltage regulator. when the alternator is stopped and the ignition is off, the regulator shuts off all current to the rotor, and there is no drain. The regulator's #1 terminal in this condition appears as a ground. When the ignition is turned on, but not started, electricity from the key ignition goes to a small filament type light bulb. The ground for this bulb is the #1 terminal, so the bulb lights up (the same as when the car key is on and the dash light (ALT) lights up). When the regulator senses this new found voltage applied to its #1 terminal, it is ready to start giving the rotor electricity to make magnetism. When the alternator begins to turn, as the engine starts, the regulator turns on the voltage to the rotor, and changes the #1 terminal from a ground to 12v positive. Now there is 12v from the ignition on one side of the bulb, and 12v from the regulator on the other, and the bulb goes out. There is positive 12v on both terminals of the bulb, so nothing flows through it. Inside the alternator is a complex array of diodes (one way check valves for electricity) this array changes the alternating current from the windings in the alternator housing, to direct current to charge the battery, and feed the regulator some charging information. The #2 terminal on the alternator is connected to the output so the regulator "understands" how much voltage is being created, and regulates it correctly. When the ignition is shut off, the light bulb has no voltage on the ignition side, and that now appears to the light bulb as a ground because it is connected to the coil through the ignition wiring. The light cannot flow enough electricity to make the coil function, so the engine stops running. If the light was not there (or a diode or resistor) there would be enough electricity coming from the #1 terminal to keep the ignition on, and the engine would not shut off.
I cannot make this simpler, and actually explain it, so I will move on to what happened to your's. First the fact that your tractor did shut off tells me that there is either a resistor, light bulb, or diode placed in the circuit (called Exciter circuit). The fact that the battery went dead is probably related to failed diodes in the Array I spoke of earlier. When a diode fails it has two options it can be like a switch that is off, or it can be turned on in both directions (shorted). if turned off, the alternator can still work some with reduced total output. If shorted, it lets battery voltage flow the wrong way through it to ground and discharges the battery when the tractor is shut off. So it is possible that the alternator failed much earlier but had enough output to keep going, then failed radically and died. It is also possible that there is a diode, resistor, or hidden light bulb in the exciter circuit. If you put a good alternator in it (three wire same as it was) it will probably be fine. If it still discharges, there may be no bulb, diode, or resistor, and it might not shut off. Replacing the amp meter is easiest, and at this point necessary to make sure it is charging. Jim
Upload one or more videos to your post. Photo and video filesizes should be less than 5MB. Formats allowed are gif, jpg, png, ogg, mp4, mov, and avi. Be sure to use filenames without spaces or special characters, and filetypes of 3 digits lower case.
We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]
Today's Featured Article - New Life for an Old Allis - by Tyler Woods. My friend Jon, has an old '39 Allis Chalmers B. He thought it a marginal tractor that had long since served its time. She smoked terribly and never had much power but he couldn't afford another so he was limping along with what he had. Jon's Allis has a small front loader and though it doesn't carry much, it serves his needs. It was the hard starting and low power that made him think it was time to replace the old girl. Jon called me to help him discover why his tractor wouldn't start
... [Read Article]
Latest Ad:
Sell 1958 Hi-Altitude Massey Fergerson tractor, original condition. three point hitch pto engine, Runs well, photos available upon request
[More Ads]
All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy
TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.
