ballast resistor

jim buford · Aug 7, 2016

I have an old Super C Farmall and there is a ballast resistor hooked to the alternator (not a generator). Why is it located there and how
should that be wired? Thanks

Hayfarmer · Aug 7, 2016

I saw a Ford tractor, older one but had alternator and had some type resister on alternator as tractor still had 6 volt battery, lights etc. but used alternator to charge. That may be what you have.

old · Aug 7, 2016

That is one of a number of ways to make it so the alternator does not cause run on when you shut the ignition off. With out it or a light bulb or diode when you shut the ignition off the alternator would back feed the ignition system and if it does that well it will run till it runs out of gas or you do something else to make it shut off

John M · Aug 7, 2016

Is it wired into the alternator, or just mounted there for the coil possibly? (Although I'm not sure why someone would mount it there for the coil.)

Bob · Aug 7, 2016

As the others have said, without more info we can't tell you what it's for.

Could either be for the ignition system and that was a convenient place to mount it or it could be used as a current-limiting resistor for the alternator's "excite" circuit.

Geo-TH,In · Aug 7, 2016

Old, without more info or a pic, it could be possible someone used a resistor in place of an idiot light to excite the alternator. Nothing to do with the ignition. Just a wild guess. Also possible someone doesn't know the difference between a resistor and a diode. Need more info before one can say for sure, only speculations.
geo

old · Aug 7, 2016

It can well have a lotto do with the ignition because if it is in the excite wire of the alternator with out it or a diode etc you can not shut the engine off.
But yes the way he asked it could also be a ballast resister in the ignition or excite circuit

Geo-TH,In · Aug 7, 2016

All you have to do is run the power to resistor through switch. I run both of my wires to alternator through switch. Doesn't matter if it's a diode or idiot light. A idiot light is a resistor too. We. Are only guessing, need to really see how it's wired.

Could be coil ballast too.

John T · Aug 7, 2016

Jim, you ask "there is a ballast resistor hooked to the alternator (not a generator). Why is it located there and how should that be wired?"

Iffffff when you say "hooked to the alternator" you mean its wired say between a 3 wire 10SI alternator (1 or R small terminal) and the ignition switch (IGN out) or coils small + input terminal ITS THERE SO THE ALTERNATOR RECEIVES INITIAL EXCITATION VOLTAGE PLUS TO PREVENT RUN ON SO THE TRACTOR DOESNT KEEP RUNNING WHEN THE IGNITION IS OFF. Those are typically small 5/10 or more ohms low power rated resistors NOT high power ignition ballast resistors.

If it just happens to be mounted there and actually wires in series between the ignition switches IGN output and the coils input (NOT wired to alternator) and is a power rated resistor (maybe 1 to 2 or so ohms) its a VOLTAGE DROPPING (12 to 6) IGNITION BALLAST RESISTOR in cases where a 12 volt tractor uses a 6 volt coil.

Got it??

John T

ballast resistor

jim buford

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Hayfarmer

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old

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John M

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Bob

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Geo-TH,In

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old

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John T

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