I bought a used Ford 1210 compact tractor and it will not start with the key. I replaced the switch and still no luck. Tested the safety switch & wire that goes to the starter and both are in good order (verified with ohm meter). When I try to start with the key, the lights dim some so I can see that something is happening.

If I jump the contacts on the starter solenoid directly, the tractor will fire right up.

But, then I cannot turn it OFF with the key either!

Perhaps you have the wrong switch.

Got it fixed - the contacts were just corroded. But, I can still turn the key off and remove it and the tractor will stay running until I pull the throttle all the way down...