Follow up on H that wouldn't start

Charlie M · Jun 15, 2014

Last night I posted how my H suddenly wouldn't start and it had no spark. Got into the problem this morning. Couldn't get a voltage reading on the resistor. Its a 6-12 volt conversion I did way back in 1988.Fortunately I had a spare one on hand and after I put new ends on the wires and hooked it up the tractor started right up as normal.I have 3 tractors converted that way and this is the first resistor I've had go bad.If I ever have to replace the coil its going to be a 12V coil and get rid of the resistor - its just one more thing that can go bad.

rustyfarmall · Jun 15, 2014

(quoted from post at 07:42:22 06/15/14) Last night I posted how my H suddenly wouldn't start and it had no spark. Got into the problem this morning. Couldn't get a voltage reading on the resistor. Its a 6-12 volt conversion I did way back in 1988.Fortunately I had a spare one on hand and after I put new ends on the wires and hooked it up the tractor started right up as normal.I have 3 tractors converted that way and this is the first resistor I've had go bad.If I ever have to replace the coil its going to be a 12V coil and get rid of the resistor - its just one more thing that can go bad.

My thoughts exactly. In fact, if I were to do a 12 volt conversion today, I would toss the ballast resistor and go with an internally resisted 12 volt coil.

pete 23 · Jun 15, 2014

Depends on the model of tractor. If it has provisions on starter to by pass resistor for starting you will have a better system using the external resistor. That is why IH and many other manufacturers do it that way.

notjustair · Jun 15, 2014

I only have one around here with a resistor. I bought it that way and have just been too lazy to fix it. Seems like another place for the wasps to build a nest.

David G · Jun 15, 2014

Nice to hear you diagnosed the problem without throwing parts at it.

Good job.

mkirsch · Jun 16, 2014

(quoted from post at 10:15:33 06/15/14) Depends on the model of tractor. If it has provisions on starter to by pass resistor for starting you will have a better system using the external resistor. That is why IH and many other manufacturers do it that way.

Why is it a "better system?"

The reason for the 12V bypass is because the voltage drops, sometimes dramatically, when you are cranking over the larger engines. A 6V coil will not fire on 4V, but it will fire on 10V.

Keeping the coil 6V and bypassing the resistor during starting was just a hack by IH to keep from having to put in a bigger battery and cables that could handle the job.

pete 23 · Jun 16, 2014

So how good is a 12 volt coil firing when the cranking voltage drops to 9 volts. With the bypass and a resistor a 6 volt coil will give you a much hotter starting spark at that 9 volt input. IH surely wasn't the only one to go the resistor route versus straight 12 volt coil.

Follow up on H that wouldn't start

Charlie M

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rustyfarmall

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pete 23

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notjustair

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David G

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mkirsch

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pete 23

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