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Magneto kill switch with negative ground

C

Cdog2cool4u

Member
I'm converting my Farmall B with a magneto to a 12v system with negative ground. My understanding is that 12 vs 6 volt does not affect the magnetos ability to function as it is independent of the battery. Should I still connect the kill switch to ground to shut off the tractor
and or does positive ground vs negative ground affect the function of the switch? Thank you all for your advice.
 
(quoted from post at 20:49:22 10/24/23) With most push/pull switches you will find they have to be in to run and out to kill.
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That's because most push/pull switches are designed for battery/distributor ignition. But you can still get magneto switches where out is run and in is stop. I believe I got mine from Steiner's.
 
Cdog welcome to YT. Although the term ..ground.. is a true and proper description of the action of a magneto kill switch in this case it leads to confusion. In more technical terms the kill switch is completing a circuit. The kill wire connects to the contact point circuit in the magneto. When you push in the button the contacts in the switch make a contact back to the chassis. The base of the points contact set that does no move is connected to the magneto housing, which connects to the engine and chassis. The kill wire connects to the moving part of the contacts of the points ..the breaker arm.. that opens and closes the primary circuit. When you push the button in the breaking part of the circuit becomes solidly connected or is ..closed.. to the chassis through the kill wire, this disables the function of the breaker points and ignition spark is stopped. As was said, this function has no connection to the battery or its polarity. Hopefully, that is not a failed explanation. Would probably be more clear with some diagrams.
 
Mornin Sir, good questions:

My understanding is that 12 vs 6 volt does not affect the magnetos ability to function as it is independent of the battery.

CORRECT

Should I still connect the kill switch to ground to shut off the tractor and or does positive ground vs negative ground affect the function of the switch?

YES you still connect the kill switch terminal to case/frame/ground REGARDLESS if battery is POS or NEG grounded. Of course you still need a correct switch so the OFF or KILL or STOP position is what connects the mag to case/frame/ground...

John T
 
You will want a switch to disconnect the alternator from the battery when tractor is shut down so it does not drain the battery after shut down.
 
All as I understand this is the alternator will be your problem and need 2 TWO switches to operate the tractor, one to shut off the alternatore and the second the tractor. All the advice is good for generator conversion but not for alternator conversion. If I am wrong please correct me. Had mags but orignal generator and stayed with the 6 volt. All directions to convert to alternator confuses me.
 
I have 3 tractors that are 6 volt with magneto and an alternator, 3 wire setup, no extra switches needed on mine and I don't disconnect the battery and I have no issues. Even when they sit for a few months.
 
(quoted from post at 18:45:07 10/25/23) All as I understand this is the alternator will be your problem and need 2 TWO switches to operate the tractor, one to shut off the alternatore and the second the tractor. All the advice is good for generator conversion but not for alternator conversion. If I am wrong please correct me. Had mags but orignal generator and stayed with the 6 volt. All directions to convert to alternator confuses me.
Click to expand...

Wouldn't a DPDT switch do the job. One pole would short the mag to ground in the off position. The other pole would turn off the electrical. I've seen Dad kill our "C" Allis Chalmers with magneto and no battery by choking it. You could also kill it by putting it in high gear and letting out the clutch.
 
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