My 196x Farmall 140 tractor discharges its battery, over a few of days, when the ignition is off. There really isn't much to the whole electrical system, a starter, an internally regulated Delco alternator, a keyed ignition switch and a starter button. The battery tests good using a load tester and the alternator puts out 14.4 volts. If I remove the battery cable when the tractor ignition is off, the battery does not drain. Any suggestions how to find the slight battery drain? Can an alternator defect cause a drain, perhaps in its diode pack?
Good battery discharging when tractor is off
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An alterator problem can certainly drain the battery.
Also: if you know how to use an ammeter (or multimeter with DC ampere reading), check to see if it's drawing current when the machine is off.
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I see a lot of those internally regulated alts that have power when the key is off. This will drain the battery pretty fast because the field is always energized.
Easy to check. With the key off you should have 12v to the big wire on the back, then no power to the wire on the plug closest to the big red wire on the back and you can have 12v to the wire next to that one and thats ok. If all 3 have 12v with it off that is your problem.
Or just unplug the plug and see if it fixes the problem, don't forget to plug it back in before running it.
Easy to check. With the key off you should have 12v to the big wire on the back, then no power to the wire on the plug closest to the big red wire on the back and you can have 12v to the wire next to that one and thats ok. If all 3 have 12v with it off that is your problem.
Or just unplug the plug and see if it fixes the problem, don't forget to plug it back in before running it.
If the "cause" of the discharge can't be readily found...just place one of those quick disconnect terminals on the battery (screw type or blade type)...Walmart has them for about $7.
Ranger has the most practical fix/answer.
You could also disconnect separate systems/wires, and see which one is the culprit.
You could also disconnect separate systems/wires, and see which one is the culprit.
If you have a 3 wire alternator (output, sense, excite) then someone may have swapped the sense and excite wires. The sense wire can be left conencted all the time, but the excite wire should only be connected when the key is on.
If they were swapped, then the alternator would charge just fine but would drain the battery when the engine was not running.
Feel the body of the alternator after the engine has cooled down and see if it feels warmer than other metal parts of the engine.
If they were swapped, then the alternator would charge just fine but would drain the battery when the engine was not running.
Feel the body of the alternator after the engine has cooled down and see if it feels warmer than other metal parts of the engine.
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This is probably not your situation, but I am needing to replace the battery in my Ford 8N tractor today. Just yesterday I noticed that the neighbor's sprinkler is out of alignment and is spraying directly onto my tractor. And now I have a dead battery. I don't know if the two events are related. Perhaps the excess moisture could cause a temporary short?
It wasnt mentioned but I'd bet because it's a tractor that it's a 1-wire self-exciting alternator and not a 3-wire alternator.
A good point was made though about the excite wire being hooked up to the battery side and not the keyed ignition side.
Simplest thing I would think is if you have a multimeter, you can by a decent one from sears for $20 or less even, is measure current draw between battery + post to + battery cable (with cable disconnected of course) and see what you get. Then, disconnect all electrical wires to alternator and see what kind of draw between battery and cable, this will tell you if it's the alternator causing the draw. Otherwise, good luck hunting.
It may be the ignition key especially if it's completely exposed, water can get in there and cause it to short, have seen that a lot on boats. you can disconnect the battery wire to the B side of the ignition key and then check the current draw from battery + to cable to find out.
A good point was made though about the excite wire being hooked up to the battery side and not the keyed ignition side.
Simplest thing I would think is if you have a multimeter, you can by a decent one from sears for $20 or less even, is measure current draw between battery + post to + battery cable (with cable disconnected of course) and see what you get. Then, disconnect all electrical wires to alternator and see what kind of draw between battery and cable, this will tell you if it's the alternator causing the draw. Otherwise, good luck hunting.
It may be the ignition key especially if it's completely exposed, water can get in there and cause it to short, have seen that a lot on boats. you can disconnect the battery wire to the B side of the ignition key and then check the current draw from battery + to cable to find out.
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