[Swartb]

Background. Bought a 68 140. Magneto coil/points ignition. Tried to start to see if engine would run. No spark. Noticed the coil wire was fried. Bypassed mag and started with a battery coil. Took the tractor apart and started a restoration. On to wiring and ignition switch. Has an Indak (marked in casting) 4 prong that seems to best match their

G451A​

Special​

9/16-24​

.310″​

PE(4)​

2962510​

D+G/None​

None/B+C​

None/B+C+S​

1,2,9​

It has no G terminal only B,C,D and S. But is one of two available on the list with one drain hole. . According to the manual (and the connectors) the wires are aligned as:
D= Purple wire, S=White wire, B=Black wire, and C=orange wire.
In the off key position none of the terminals show continuity with any terminal or the case. Note 2 indicates the switch is case grounded.
In the run key position, B+C are connected and in start B+C+S are connected. There is continuity in the harness for the white wire on terminal S to the engine connector for coil.
The switch is not new and looks like it has been there for awhile. Not saying it is the right one. But,
1. How could you ground the white wire if there is no ground continuity on the off position and
2. Would not the B+C+S run position provide power to the white S terminal and fry the coil wire?
3. Does this sound like the right switch?
Anyone have a diagram of the back of the switch or have an idea. The manual doesn't go into much detail.

 

[dhager4692]

AM102543 is the switch Deere specifies for the magneto tractor. I couldn't find an image of it.

 

[ed_lincoln]

Several years ago, I converted a 68 110 side tag to external coil, The 4th prong is hot only when the key is on, that's where I got the power to the coil from. .

 

[Swartb]

Thanks for the responses. I found one picture of the AM102543 at a JD dealer, but no indication of the post IDs or functions. It appears to be a 4 post switch. Cost is about $60. I ordered a new magneto 5 post switch from Isavetractors and a new 5 post connector and pins, They identify the posts and the off, run, start functions of the switch. They say, "Ignition Key switch for Battery Ignition Kohler K and Magnum Series Engines This is a 5 Terminal, 3 Position Ignition Switch. Works for all Vintage Garden Tractors and Kohler K Series and Magnum Engines that use a Magneto Ignition System The terminals are for Battery, Ground, Lights, Starter, Magneto Fits all Magneto Ignition Kohler K Series and Magnum Engines! For all models of tractors. The terminals are for Battery, Ground, Lights, Starter, Magneto 5/8" Mounting Hole Circuit Design: Off: Magneto + Ground Run: Battery + Lights Start: Battery + Start + Lights Fits all Magneto Ignition Kohler K Engines! For all models of tractors. Cub Cadet John Deere Wheel Horse Ford Jacobson Case Ingersoll Gilson And Many Others!
Can always change if I don't like it! But as a minimum don't want the Magneto wire connected to anything but ground for off position only.