418-A Won't shutoff

[Sirtowsalot 1]

Howdy y'all!

I'm having some trouble with my 418-A. I think it is ignition related, but I'm not completely sure. It starts and runs perfectly fine, but when I go to turn it off, it doesn't work. I can just turn the key into the 'off' position and take the key out while the tractor is still running and it will continue to run as if I hadn't turned the key off.

 

I'm trying to keep this tractor as original as possible, so I don't really want to buy a new ignition. Any help is appreciated. Thanks!

 

*EDIT*

Wheel Horse 418-A

Kohler Engine

18 HP

Model No. M18QS

Spec. No. 24510

Serial No. 1619706606

Edited June 29, 2018 by Sirtowsalot
Added additional details.

[gwest_ca-(File Mod) 12,051]

You have magneto ignition which is self-powered and the single ignition wire just needs to be grounded to the chassis metal or negative battery to shut the engine off. Do not allow any battery power into that wire.

Could be ignition switch, pto switch or seat switch.

With the engine running, pto engaged and you leave the seat the engine should quit. Seat switch should ground the ignition wire. That may help narrow the problem down. The body of the ignition switch should be grounded also so the key will shut it off.

Garry

[Sirtowsalot 1]

Thanks for your response Gwest_ca!

 

The only method I can find to shut off my wheel horse is to pull the spark plug wires. The seat switch won't kill it either.

 

The ignition switch I have only has terminals labeled as : A, M, B, R, S, and 3

 

KEY OFF: A+3, A+M, 3+M

KEY ON: A+B, A+R, B+R

KEY START: B+S

 

3 is the slanted pin on the bottom right.

Edited June 29, 2018 by Sirtowsalot

[gwest_ca-(File Mod) 12,051]

Click on the picture. One of the next ones that come up show how to test each function of the switch.

#3 is for a ground wire to the chassis. When dash panels were changed to plastic panels simply mounting the switch in the panel did not provide a ground.

I would check for a bad connection in the ignition wire starting at the engine and work your way back to the ignition switch.

Any chance a mouse has chewed the wire off under the engine tins?

Garry

[Sirtowsalot 1]

Sorry for the late response,

Where would I start to trace the wiring back from the engine? And yeah, there is a good chance that a mouse may have chewed one of the wires. I'll go attempt to locate the broken wire.

[pfrederi 20,036]

Find the 3 wire connector like in first picture.  Separate it  The use you rmultimeter set for continuity to probe the top right terminal and the other on the frame or other ground.  With the key switch in the off position you should have continuity (almost 0 resistance)..  If you do not then there is a problem in the switch itself or the wire from the connecter to there.

[Sirtowsalot 1]

Thanks Pfrederi, I'll give that a try.

If you don't mind me asking, what kills the mower when the switch is turned off?

[pfrederi 20,036]

That wire comes from the magneto.  if it is grounded the mag stops making spark.  If it is not grounded she will continue to run.  Do not under any circumstances apply voltage to the engine side of that wire connector  you might have very expensive smoke from your magneto

[Sirtowsalot 1]

Thanks for the help everyone. 

I found the black wire with a blue stripe chewn in half... damn mice. I put it back together with a butt connector and it shuts off just fine now!

Wohoo!