Kill Switch

Two Banger · Mar 10, 2010

I have purchased a kill switch from Denny's Carb and am trying to figure out how to wire it. I have a positive ground system with electronic ignition. The switch is a normally open switch. The directions say to hook one wire to the frame and the other wire to the positive side of the coil. This is already done at the coil location, so this won't kill anything. I contacted Denny's numerous times without much help. Finally they said to hook one wire to the frame and try hooking the other to the negative side of the coil, thus grounding out the coil when the switch is activated. I am a little nervous about trying this, don't want to fry my new hot coil or my electronics, any thoughts out there.

sflem849 · Mar 10, 2010

Don't buy stuff from Denny's and a normally closed switch would be a lot easier to wire. You asked for thoughts...

ScottyHOMeY · Mar 10, 2010

Nope. With any battery powered ignition (as opposed to a magneto) a double pole switch should be wired in-line, between the battery and the ignition. One wire from battery power, the other running to the ignition.

For original style Farmall swithches, there were two types. For magneto ignitions, the switch had a single pole on the bottom. From that pole a wire ran forward to a stud on the side of teh magneto. With the switch button in thee "up" "RUN" postion the switch was open. When pushed down to the "STOP" position the switch was closed, and stopped the motor by gounding the magneto. Ground was reached through the body of the switch being mounted to the chassis.

The otherwise identical (for outside appearance, anyway) switch for battery ignitions had two poles on the bottom. In that case the switch was closed in the up postion, allowing the juice to flow from the battery (one pole of the switch) to the ignition to the pole connnected to the igntion coil. Pushing the switch down opened the connection, breaking off power to the igntion to stop the motor.

If your switch has to poles on it, one should run to a battery source, the other should run to your ignition.

sflem849 · Mar 10, 2010

(quoted from post at 20:16:11 03/10/10) Nope. With any battery powered ignition (as opposed to a magneto) a double pole switch should be wired in-line, between the battery and the ignition. One wire from battery power, the other running to the ignition.

For original style Farmall swithches, there were two types. For magneto ignitions, the switch had a single pole on the bottom. From that pole a wire ran forward to a stud on the side of teh magneto. With the switch button in thee "up" "RUN" postion the switch was open. When pushed down to the "STOP" position the switch was closed, and stopped the motor by gounding the magneto. Ground was reached through the body of the switch being mounted to the chassis.

The otherwise identical (for outside appearance, anyway) switch for battery ignitions had two poles on the bottom. In that case the switch was closed in the up postion, allowing the juice to flow from the battery (one pole of the switch) to the ignition to the pole connnected to the igntion coil. Pushing the switch down opened the connection, breaking off power to the igntion to stop the motor.

If your switch has to poles on it, one should run to a battery source, the other should run to your ignition.

That's what I was thinking when I said it would be easier to wire a normally closed switch. I would use a boat kill switch, but it is too late now. I have NO idea how to wire a normally open.

ScottyHOMeY · Mar 10, 2010

I agree. The "normally closed" description is a little confusing. I grew up tih the old ST/DT, SP/SP nomenclature, which (I hope) still has some validity as such conversations go. To my ear, "normally open/closed" indicates a swith that requires a momentary action to make or break the circuit. It doesn't apply to switches with two defined positions.

Bottom line, if what Two Banger has in hand is an original style Farmall switch, he will need the two pole type designed for battery ignitions, which will have two poles on the bottom, both of which are insualted from ground. The single-pole type of the original Farmall switch, intended for magneto ignitions, grounds through its body, and does not provide any continuity (in either position) between a source of battery power and the igntion.

Bob · Mar 10, 2010

Connect the switch to chassis ground and the points side (EI side) of the ignition coil.

Switch closes, it's just like the points never open (or the EI's shorted out )and the engine will die.

Of course, those of us that grew up around hay balers or swathers with Wisconsin engines will have an easier timer understanding this than the rest of you!

(Those suckers had a cylinder head temp switch that would close and "kill" them if they overheated.)

sflem849 · Mar 11, 2010

(quoted from post at 20:48:56 03/10/10) I agree. The "normally closed" description is a little confusing. I grew up tih the old ST/DT, SP/SP nomenclature, which (I hope) still has some validity as such conversations go. To my ear, "normally open/closed" indicates a swith that requires a momentary action to make or break the circuit. It doesn't apply to switches with two defined positions.

Bottom line, if what Two Banger has in hand is an original style Farmall switch, he will need the two pole type designed for battery ignitions, which will have two poles on the bottom, both of which are insualted from ground. The single-pole type of the original Farmall switch, intended for magneto ignitions, grounds through its body, and does not provide any continuity (in either position) between a source of battery power and the igntion.

Yes all that throw pole technology is still around, but this isn't a normal switch. He got a kill switch to be used IN ADDITION to the ignition switch on the "dash." This is used if he comes unhooked from the sled so the tractor doesn't run away.
All the switches your referred to (SPDT, DPDT, etc) would be normally closed switches. SO when in the on position the circuit is completed. The one Denny's sold the guy is normally open, therefore the circuit is not completed when the switch is on.

Two Banger · Mar 11, 2010

I guess I sent out a little bit of confusion with this one. Sflem849 hit it just right. This is not an ignition switch. It mounts to the back of the tractor to hook a cable to while competing in tractor pulls. In the normal state (pin in) there is no circuit made, if a break a way occurs (pin pulled out) it makes the circuit. I agree one that works the opposite would be a lot easier to wire. Unfortunately all break a way switches that I have found work like this one. Will I hurt anything if I ground out the coil? Seems like to me a dead short across the coil would not be a good thing. A magneto is a completely different animal though.
Thanks

sflem849 · Mar 11, 2010

(quoted from post at 15:11:36 03/11/10)
I guess I sent out a little bit of confusion with this one. Sflem849 hit it just right. This is not an ignition switch. It mounts to the back of the tractor to hook a cable to while competing in tractor pulls. In the normal state (pin in) there is no circuit made, if a break a way occurs (pin pulled out) it makes the circuit. I agree one that works the opposite would be a lot easier to wire. Unfortunately all break a way switches that I have found work like this one. Will I hurt anything if I ground out the coil? Seems like to me a dead short across the coil would not be a good thing. A magneto is a completely different animal though.
Thanks

I got called a dick yesterday so I might as well keep it up

You better not be the guy I listed a complete website of kill switches for last month!!!

Here is one that can be wired either way. Maybe it is too expensive...esp when compared to Denny's. (For those who don't look at the link, it is only $6.95) Maybe you just can't get over Denny's incredible customer service :lol: :lol: :lol:
http://www.jmsonline.net/safety-kill-switch-universal.htm

Your best bet is to look towards the marine industry. I would send that POS back to Denny and tell him he is a moron for selling you a normally closed switch for a coil tractor!!! He knows damn well they are for magnetos only. Just Google "marine kill switch" and there are 217,000 hits and the whole first page is full of some quality ones. I like to use the shopping tab as well.

I have no idea how you can make the one you have work. Maybe some of those marine kill switch threads will inspire you. Boat motors were on mags a while longer than tractors were so there may be more people who know how to do it. I'm off to Denny's to see how bad you got ripped off.

sflem849 · Mar 11, 2010

$29.95 Not as bad as I would have thought. Does this look familiar?
http://www.pacificrvparts.com/ProductDetail.asp?ProductID=30567&StoreID=41&DepartmentID=175&CategoryID=318
It is a trailer breakaway switch. They are designed to complete the circuit and send 12v power to the brakes when the trailer comes off the ball. It couldn't be normally closed or it would apply full brakes all the time.

Kill Switch

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