M starter switch

Farmall M, Super M, 400, 450 & 560 Tractors, 1939-1963

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M starter switch

Postby JBall8019 » Sun Jun 11, 2006 11:43 am

i have gone through enough starter switches for my m now. damn cheap things. has anyone found a large amperage push button switch to replace thiers?? i am at my limit of paitence with damn switch!!!! i really need some help!
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Postby Bigdog » Sun Jun 11, 2006 1:53 pm

John - take one of them apart and look at the contact surfaces. Sometimes you can dress them to clean them up and provide more contact surface. Most of them fail because instead of contacting the broad contact surface, they touch only on a small point.
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Postby allenlook » Sun Jun 11, 2006 2:35 pm

Mine have failed in the past due to arcing/pitting. Seems when the contacts come apart they give a "zap" and a puff of smoke and lose a little more copper from the thin zone that contacts on each edge of the copper "button" inside.

I was just looking inside mine today from the Cub trying to figure out a better way to make contact in there, with fingered contacts instead of just a lump of copper like it uses...

I haven't figured out anything yet. :?
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Postby JBall8019 » Sun Jun 11, 2006 10:07 pm

thanks guys, my neighbor came over and fixed the switch. he welded something in it for me. he said that the switch is the same one in his ford and they are junk. i will be looking for something else in the meantime.
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Postby Matt Kirsch » Mon Jun 12, 2006 9:11 am

It's not really the quality of the switch that is the problem; it's the fact that the switch is the ABSOLUTE WRONG TOOL FOR THE JOB.

These switches have been a thorn in farmers' sides since at least 1939 when the first M hit the showroom floor.

The problem is that a human can't possibly push the switch quickly enough to keep an arc from jumping across the contacts. Eventually, the two surfaces get burned badly enough that the switch doesn't work anymore.

This is why they went to solenoids. Solenoids can close the gap quickly enough that little or no arcing occurrs. They still burn out, but they last a lot longer than those switches.

You can mount a solenoid on your starter, and eliminate a bunch of battery cable. Plus the system is a whole lot more reliable.
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Postby JBall8019 » Mon Jun 12, 2006 11:06 am

ok matt how does someoneone mount a solenoid to the starter? :) i will try that is its easy to do!
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Postby Bigdog » Mon Jun 12, 2006 11:24 am

John, you can mount the solenoid to the steering wheel support post or any convenient location and connect the cables that currently run to the heavy duty starter switch to the solenoid terminals. You will then need to connect a switch circuit to energize the solenoid. This can be a key switch, push button or you can even use the original starter switch to control the solenoid. 1 hot lead to the switch and then from the other terminal on the switch to the solenoid primary terminal. If the primary coil on the solenoid has 2 terminals - ground the other one. Most are already grounded through the mounts.
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Postby Matt Kirsch » Mon Jun 12, 2006 3:02 pm

BigDog's right. You can mount the solenoid anywhere. It's just that the starter is where Dad put one on his Super M, and it's where solenoids are usually mounted on most modern engines.

The arrangement of putting the solenoid on the starter also eliminates quite a bit of battery cable. Shorter cables lose less power, and you'll see a marked improvement in how the tractor turns over if it's a little "iffy" right now.

You may need to drill and tap two holes on the case of the starter, or use a long hose clamp to mount the solenoid to the starter. Dad did his when I was very young, and I don't recall how the holes got in the starter case. I do know you have to be VERY careful when drilling and tapping to keep from nicking the field windings.

With a little creatitivty, you can even hide the solenoid somewhere and use the original starter button to activate the solenoid, so it looks "original." The starter button will last forever activating the solenoid.

Basically, it's:
1. Main battery cable to big terminal on solenoid.
2. Other big terminal on solenoid to starter.
3. Ignition switch to one side of the starter button.
4. Other side of the starter button to the little post on the solenoid.
5. Other little post on the solenoid (usually marked ground, if equipped) to a suitable ground.
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Postby JBall8019 » Mon Jun 12, 2006 9:21 pm

hey mattt and bigdog,
that doesnt seem too bad of a job, and also doesnt seem to cost much either. solenoids are around $15 for a ford at tsc.
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Postby Bigdog » Mon Jun 12, 2006 9:34 pm

Easy job John.
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