I have 1964 JD 1010 Diesel, at least I think it is a 1964 because cannot find a serial number on it anywhere. Using the shop manual as a guide my best guess is a 64. Here is my problem.
Went to start my tractor put when I release the key the starter continue to spin. Had to disconnect the battery cable to get it to stop. Found a broken thermal on the key switch so I got a new one, same problem. I then jumped to the conclusion it was the solenoid so I got a new one, same problem.
Next, I did some research and decided to take the starter off and bench test it. It worked perfect on the bench. I used a battery, jumper cables and small wire with clips to jump the solenoid on the bench. Put the starter back on the tractor and used just the jumper cables and small wire to engage and guess what, the starter continue to spin after I removed the small wire. Then I had two auto mechanics go through the same things and they left scratching their heads. I unhook all the wires on the tractors and still got the same results. I am out of ideas. Why would it work on the bench but not on the tractor? BTW, it is a reverse polarity system.