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PaulC

Magneto ignition switch on coil ignition system

By PaulC, in Wheel Horse Electrical

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PaulC    341

PaulC
Posted

What happens if you install a ignition switch for a magneto style ignition on a battery/coil based ignition system?

I just picked up 2 417-a's that neither will turn over with the ignition switch, both have a jumper wire hooked to the bottom post of the solenoid that you need to touch to the positive side of the battery to get the tractor to turn over. Ive only been able to get 1 running and I purchased a new ignition switch for that one hoping to be able to eliminate the jumper wire. After installing the new switch I still have to use the jumper wire. In the run position on the switch everything works and the tractor starts and runs fine with the jumper wire but if I disconnect the jumper wire and use the actual tractor wiring the motor will not turn over when the key is switched to the start position. Ive now just realized the new switch I purchased was part number 103991 for a magneto based system instead of 103990 for the coil ignition.

Given what I just laid out if I buy the correct ignition switch should the engine turn over from the switch? From the searching ive done it seems like the tractor shouldn't run at all with the 103991 switch?

I also have a 87 312-a with a  kohler magnum which is the magneto ignition system and that tractor has a push button wired in to essentially do the same thing jump the bottom post of the solenoid to the battery, I bought it this way and its always worked. Im now thinking maybe the switch I just bought for the 417 will fix the issue on the 312.

If I am wrong on all or any of this please correct me and what else besides the ignition switch could be the culprit?
 

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pfrederi    17,849

pfrederi
Posted

The difference between mag switch an  coil switch is the M vs I terminals.  M is used to ground the mag and kill the engine and is only connected with the key in the off position..  The I terminal provides electricity to the coil when the switch is in run and start position.

Both should provide voltage out the  S terminal in the start position and that should trigger your starter solenoid.

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Save Old Iron    1,566

Save Old Iron
Posted (edited)

Apparently there are starter circuit wring issues on both tractors. Both style switches have similar functions for CRANKING the engine. The support they provide for the ignition circuit is completely incompatible and non interchangeable. Using a coil based switch in a mag based tractor can and will burn out the magneto assy.

103991 will work on the magnum engine. By itself, it may not resolve your starting issues if you have additional safety switch or wiring issues.

Edited by Save Old Iron

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PaulC    341

PaulC
Posted

Ok i figured it wasn't going to be that easy. So the 103991 should work correctly on a battery or magneto ignition system? Glad i didn't go battery switch on magneto system.

Guess im going to have to do some more digging, I don't mind the push button solution like the PO did on my 312 but i would rather have it work as its supposed to. All the safety's on the 417 seem to be working correctly except for maybe the clutch/brake switch? That light on the dash stays on always and if that was the issue i would guess i would have no spark not lack of cranking through ignition switch? My other 2 hydro tractors i don't think have that safety switch and i definitely don't need to depress the brake pedal to get them started?

Thanks for the help guys

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Save Old Iron    1,566

Save Old Iron
Posted (edited)

 So the 103991 should work correctly on a battery or magneto ignition system?

​Incorrect.

Maybe I misspoke.The ignition switches do share common internals for the STARTER function and the ACCESSORY function. For IGNITION and OFF, they are different. A coil based switch will connect 12 volts to the "I" terminal in START and RUN positions. If you were to connect a magneto to the "I" terminal, the low resistance winding in the mag would overheat and be destroyed in a few seconds.

Use the correct switch for your application. Troubleshooting is difficult enough without knowingly handicapping your chances of a lasting fix.

https://www.google.com/search?q=103991+switch&biw=893&bih=534&source=lnms&tbm=isch&sa=X&ei=34poVdfPLoeXsAXbz4PoAQ&ved=0CAcQ_AUoAg&dpr=0.9#imgrc=9ZDcWtkTdKiFcM%3A%3B1gtD0zWPTBHtRM%3Bhttp%3A%2F%2Fi1228.photobucket.com%2Falbums%2Fee458%2FSOI_University%2F103991backterms.gif%3Bhttp%3A%2F%2Fwww.wheelhorseforum.com%2Ftopic%2F27331-414-8%2F%3B266%3B417


https://www.google.com/search?q=103991+switch&biw=893&bih=534&source=lnms&tbm=isch&sa=X&ei=34poVdfPLoeXsAXbz4PoAQ&ved=0CAcQ_AUoAg&dpr=0.9#tbm=isch&q=103990+switch&imgrc=ZRoU7eaVwhlUeM%3A%3BzoHagBGVvxa7gM%3Bhttp%3A%2F%2Fi1228.photobucket.com%2Falbums%2Fee458%2FSOI_University%2F103990switchterms.gif%3Bhttp%3A%2F%2Fwww.wheelhorseforum.com%2Ftopic%2F32973-312-8%2F%3B266%3B417

Edited by Save Old Iron

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PaulC    341

PaulC
Posted

I figured out that the clutch does need to be depressed to start these tractors. The switch must be bad because once I jumped it it fired right up with the turn of the key. 

I also got the other 417 running!! Cleaned up some electrical regapped the points and put in a new condenser. 

Thanks for the replies and help. Paul 

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