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1951 Farmall C

V

vet119

New User
Does anyone know what 12 volt starter I need for my 51 C? I converted over to 12 volt and the 6 volt starter is bad. Dont know what will fit.

Thanks
 
Not sure whats available for 12v. starters. I think most people just use the 6v starter for the 12v. conversion. Doesn't really hurt it unless you grind and grind to get the tractor started. Just a quick hit of the starter and a fire off right away type use, the 6v starter lasts along time and doesn't suffer to much damage. My 2 cents.
 
The heat generated is what harms electronics ,
rebuild ,don't , do not, buy cheap Chinese
replacements they are junk ,if your 6v starter uses
600 amps cranking it should only use 300 amps on 12v
,either way the same heat is generated.
 
(quoted from post at 17:03:59 10/08/14) Does anyone know what 12 volt starter I need for my 51 C? I converted over to 12 volt and the 6 volt starter is bad. Dont know what will fit.

Thanks
Click to expand...

Take it to an "auto-electric" shop and get it rebuilt. When you get it rebuilt, have them install 12V field windings... will cost about an extra $75 over the rebuild cost, but well worth it. I did that to my 240U and it never started so good. I can leave it set for weeks and it will fire off so fast I can't believe it.
 
I agree with you on the amps, but there are those who say when you double the voltage it doubles the amperes too. I don't see how with the cells only half as big. John T , where are you?
 
I am not an expert, but I have converted to tractors (Super "C" and "H") and used the six volt starter on both tractors.
 
The Volts and Amps thing is described by Ohm's Law, which states that there is a mathematical relationship between Volts, Amps, and Load.

Ohm's Law: Volts = Amps X Load

If you keep the Load the same, and double the Volts, in order to make the equation work, the Amps have to double. If you measure it in real life, you will see that it works out.

So long as you don't crank and crank and crank and crank and crank and crank and crank and crank and crank and crank and crank on the engine with 12V, the starter will hold up just fine. Fix the tractor so it starts easily.
 
Might want to get one of the clutch drive bendix for it also. It is not as hard on the starter and the flywheel. I took mine to an old school auto electric shop and had him go thru it. I put the bendix on myself. It has worked just fine on 12v.
 
So where do all those extra amps come from when the cells in a 12 volt battery are only half as big as a 6? And how are all those extra amps going through those skinny cables used on the 12 volt system? On the faster spinning starter, the back EMF cuts the amps down too.
 
Ohms law is actually: V=IxR, where V is Volts, I
is amperage (current), and R is the resistance of
the circuit. Resistance isn't the same as Load.
Load is measured in watts.

The formula for Watts is: W=IxV where W is
Watts, I is still current, and V is still Volts.

So if the load (Watts generated by the starter
motor) stays the same, and you double the voltage,
the current needed will be less. It won't be
exactly half, but it will be less.

That's why 6 volt battery cables have to be so
much larger than 12 volt battery cables, 6 volt
cables are carrying more current.
 
I think you nailed it as that is what is happening in the real world. The voltage is what makes the starter spin faster, not the amps. Goes to show that the magnetic field doesn't come from the current as we have been falsely taught but it comes from the atoms of the conductor excited by the voltage.
 
I usually avoid commenting on any questions relating to 12-volt conversions. But the number of posts based on poorly understood or totally misunderstood electrical concepts is truly impressive. The thread really went in a ditch about half way through. I'm not sure where to start on straightening it out, so I won't try.

To get back to your original question, your best chance at an actual 12-volt starter that will fit a Farmall C is to check the one for a late (12-volt) Farmall 140 (requires a separate solenoid to engage), or one from a Farmall/International 404 (solenoid directly on starter). As 12-volt starters are often larger in diameter that the equivalent 6-volt, there may not be clearance enough for those starters. The later tractors may have had castings modified for clearance. Check for ring gear changes as well, in case they made some incompatible change in the drive gears.

In any case, the advice already given to just rebuild your existing starter is reasonable, known to work and probably as inexpensive as any alternative.
 
Most people don't care to know the gory details about the whole thing, and no offense, but may not be capable of understanding the myriad of details surrounding the basic concepts.

Ohm's Law pretty accurately describes the BASIC relationships. Sure, it's not quite the same when you're talking about a motor vs. a light bulb, but it's CLOSE ENOUGH for the average person who has never dealt with DC electricity past pushing the starter button on their tractor.

BTW, your battery cables should actually be THICKER with 12V because they're carrying more current. The reason you can get away with thinner cables is because even with the losses due to the thin cables, the voltage reaching the starter is greater than it would be on 6V under ideal condions.
 
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