Farmall Super H battery drain

Paul in SC · Mar 14, 2011

I have a 53 Super H wired for 12 volt as per Bob M's diagram off this website. Used this layout on other tractors and works great. However on this SH, I used a new (remanufactured) Hitachi 14231 alternator with all new wiring throughout tractor. My problem: With engine off, switch off (open), there is a voltage of 2 volts, plus or minus, that drains through the "idiot" light to ground through the points (if engine stops with points closed). This kills battery over long idle periods. Is this a defective alternator?

Bob M · Mar 14, 2011

Paul - Assuming your wiring is correct, problem's gotta be a defective alternator (specifically a bad regulator inside the alternator).

Swap in a good alternator and your problem should disappear.

Paul in SC · Mar 14, 2011

Thank you, Bob M. I suspected that and I will have this unit replaced and try a different one. Thanks Again, Paul

Janicholson · Mar 15, 2011

Bob, What would happen if the idiot light was not the correct resistance. If for instance it was a headlamp bulb. could the alternator "see" this as a Key on situation and remain in the pre excite mode after shutdown but not have enough current to keep the ignition operating? If so would putting a marker lamp in place work to "fix" it?
Just thinking out loud, Jim

Bob M · Mar 15, 2011

Jim - Incorrect idiot light resistance would not cause battery drain. Reason is the idiot light circuit is open at the ignition switch when the switch is off and the alternator is not spinning.

Incorrect resistance CAN however affect alternator operation. Too high and the regulator won't "turn on" so the alternator won't charge. And too low the alternator will backfeed enough current thru the idiot light to fire the coil when the ign switch turned off. Thus the engine will not shut down.

Good question however!

Bob M

Janicholson · Mar 15, 2011

Thinking again. If the points were closed and tractor stopped, but the alternator continued to feed current to the circuit, the light would remain lit, and the battery would drain. There just might not be enough current to run the tractor ignition.
(personally I think it is an out of spec regulator in the alt) Jim

sflem849 · Mar 15, 2011

...(personally I think it is an out of spec regulator in the alt) Jim

How do you check it? My MD seems to like to drain batteries. I am not certain that it is the tractor bc I never really run a decent battery in it bc it gets very little use.

Janicholson · Mar 15, 2011

Thinking again. If the points were closed and tractor stopped, but the alternator continued to feed current to the circuit, the light would remain lit, and the battery would drain. There just might not be enough current to run the tractor ignition.
(personally I think it is an out of spec regulator in the alt) Jim

Paul in SC · Mar 19, 2011

In my original post on 3-14 concerning battery drain on SH, Bob M called it dead on right: bad alternator. I followup with this post so it may help someone else. With engine off, switch off, there was a reading of 1.5 volts going through idiot light to points. (not enough voltage to light up the lamp) When engine happen to stop with points closed, the battery was drained and went dead in two months. Tractor ran fine and ammeter indicated charging during operation. Alternator was checked by two shops and it appeared to be functioning correctly. In other words, the defective internal regulator did not show up on test bench. Alternator was replaced (at no expense to me) and functions fine now. Thanks to Bob M and Janicholson for their help. Paul

Farmall Super H battery drain

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