My Uncle has a Farmall Super A that has been converted to 12V with an alternator. Ever since he has owned the tractor he hasn't been able to get it to charge the battery. He's but 3 different alternators on and it wont charge the only way it will charge is if you override the governor and its screaming then it charges at 18V. But if you walk up to the tractor with a multi meter the needle starts jumping across the meter when your 2 feet away it goes from 2-20V it just goes wild. This tractor does have a distributor,could the voltage somehow be getting through an insulator in it causing this wild power. What could be the problem here? Thanks in advance.
- Thread starter Awilson
- Start date
mattofvinings
Member
If there's a cut in a spark plug wire all bets are off as it can be leaking high voltage to ground somewhere unexpected.
That usually shows up as a bog or fail under load though because more spark energy is needed to jump the gap as the torque/load increases.
It also sounds like a wire harness re-do is in order. There can be some cobbed up messes from when the standalone voltage regulator was removed. The wiring harness on a SA is pretty simple.
That usually shows up as a bog or fail under load though because more spark energy is needed to jump the gap as the torque/load increases.
It also sounds like a wire harness re-do is in order. There can be some cobbed up messes from when the standalone voltage regulator was removed. The wiring harness on a SA is pretty simple.
gene bender
Well-known Member
wrong alt yours needs two many rpms to start charging pulley on fan driving the alt makes this happen. Get a Delco 10si then wire from Bob Ms dia.
BarnyardEngineering
Well-known Member
- Location
- Rochester, NY
You've got electrical noise there but that won't affect the alternator.
You say he's tried 3 alternators... but did he have ANY of them wired up correctly? That is the question.
Other than the quality of cheap rebuilt alternators from the parts stores, I have had zero issues with the standard 3-wire setup using a diode and a wire to excite the alternator from the switched power side of the ignition coil. Since the alternator is on the opposite side of the engine from the coil on a Super A, it may be easier to run the wire directly from the ignition switch.
You say he's tried 3 alternators... but did he have ANY of them wired up correctly? That is the question.
Other than the quality of cheap rebuilt alternators from the parts stores, I have had zero issues with the standard 3-wire setup using a diode and a wire to excite the alternator from the switched power side of the ignition coil. Since the alternator is on the opposite side of the engine from the coil on a Super A, it may be easier to run the wire directly from the ignition switch.
One other thing that no one has mentioned is pully size.If it has a large pulley it wont spin fast enough to charge.An alternator needs the smallest pulley available in order for the slower RPM tractor engines to spin the alternator fast enough to charge.As was said,correct wireing and a good harness are very important.Sometimes an alternator needs a separate ground wire. Just allowing it to ground through the mounts isn't enough sometimes.
tn terry t
Well-known Member
I always ask for a 1980 350 chevy pick up alternator
glennp63ford
New User
As long as the ammeter is wired correctly (in line between the alternator and the battery) it shouldn't have an affect on anything
I have a 1-wire alternator on my M with a voltmeter. The voltmeter always reads 12 V when I start the tractor and after it warms up I bring the engine up to full throttle and the meter immediately jumps up to 14 V and stays at 14V even as I go back to idle. This is normal operation as the 1-wire configuration needs to reach a certain RPM to excite the field coil.
If your uncle's volt meter is not reading around 14V, even after bringing the tractor to high rpm, he may need a smaller pulley (on the alternator) to provide higher rotation. Otherwise, he can switch to a three-wire configuration which will charge without requiring high rpm.
If your uncle's volt meter is not reading around 14V, even after bringing the tractor to high rpm, he may need a smaller pulley (on the alternator) to provide higher rotation. Otherwise, he can switch to a three-wire configuration which will charge without requiring high rpm.
tn terry t
Well-known Member
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