JD 3020 D start circuit

My '66 JD 3020 Diesel starter wants to turn/engage the moment the first negative battery cable touches the post. The old 24V starter began to show this symptom when the starter began running - noticed sometime after the tractor was successfully started and working. It made quite a racket as it got hotter and hotter and continued to turn. Had to disconnect the Bat cables to make it stop. Examined the situation to find the small double-yellow wires that connect the neutral safety switch to the starter had gotten tangled up in the clutch return spring under the left floor board. Bare wires were taped up and secured in the battery cable clamp where they belonged. The starter engergizing issue continued...

Thought my starter was malfunctioning, decided to finally convert to 12V instead of fixing the 24V starter. Fast forward to yesterday, made the final connection to my 24V/12V conversion and the original problem still exists in my brand newly converted start circuit!?!?

Thanks for any helpful suggestions.

Bare neutral start wires(yellow) won't cause starter to be engaged in flywheel. A pitted washer & lugs inside solenoid cap can cause engagement or shorted wiring(bad insulation) can also. 66 3020 had a push button for start that could be the problem also.

I am thinking it could be a sticky push button.

Update - i replaced the start switch with a single pole on/off switch for trouble-shooting purposes with no affect, so it doesn't appear to be the switch.

Assuming the old starter was at fault then, and now the new 12V components aren't wired correctly which was causing the identical symptom for a different reason... i embarked on the 12V conversion with only a general schematic and no specific details on how to connect the intermediate solenoid between the starter solenoid and the switch. But on further research at my local auto parts store i discovered that the intermediate solenoid provided in the conversion kit is actually an insulated unit with two small posts used to connect one post to the switch and the other to ground to complete the control circuit, close the switch and send 12v to the starter solenoid. I do now have a functioning intermediate solenoid that closes when the start switch is engaged and there is 12v at the small post of the starter solenoid - but no luck. So there is also a second small post on the starter solenoid, not in use - so i made the leap that it too may be an insulated unit requiring an external ground, so i ran a ground wire to the same starter mount bolt used to ground the intermediate solenoid, hoping to give the starter solenoid control circuit a good ground and still have no luck.

How can the starter solenoid have 12v available to the small control circuit post, a good ground connected to the other small post and still not engage while the intermediate solenoid is clicking away freely, each time i close the start switch???? I'm at a loss - could the two small posts on the starter solenoid be polarized, requiring 12v be applied to a specific post? That re-arrangement is the only thing i have left to try, unless you folks have something else in mind?

Thanks very much for your time and patience.

Mike

Update - i replaced the start switch with a single pole on/off switch for trouble-shooting purposes with no affect, so it doesn't appear to be the switch.
Assuming the old starter was at fault then, and now the new 12V components aren't wired correctly which was causing the identical symptom for a different reason... i embarked on the 12V conversion with only a general schematic and no specific details on how to connect the intermediate solenoid between the starter solenoid and the switch. But on further research at my local auto parts store i discovered that the intermediate solenoid provided in the conversion kit is actually an insulated unit with two small posts used to connect one post to the switch and the other to ground to complete the control circuit, close the switch and send 12v to the starter solenoid. I do now have a functioning intermediate solenoid that closes when the start switch is engaged and there is 12v at the small post of the starter solenoid - but no luck. So there is also a second small post on the starter solenoid, not in use - so i made the leap that it too may be an insulated unit requiring an external ground, so i ran a ground wire to the same starter mount bolt used to ground the intermediate solenoid, hoping to give the starter solenoid control circuit a good ground and still have no luck.

How can the starter solenoid have 12v available to the small control circuit post, a good ground connected to the other small post and still not engage while the intermediate solenoid is clicking away freely, each time i close the start switch???? I'm at a loss - could the two small posts on the starter solenoid be polarized, requiring 12v be applied to a specific post? That re-arrangement is the only thing i have left to try, unless you folks have something else in mind?

Thanks very much for your time and patience.

Mike