Here is a simplified schematic for the Start Circuit for the 2072.
Here is some testing to do with a DVM or VOM.
With the meter set on a Resistance Scale (ie: Rx1, Rx10, etc) place the black meter lead on the Black Negative Battery Terminal.
Do all you test points with the Red Meter lead.
Start with taking the Small Red Wire off the Starter Solenoid. With this wiring hanging in mid air, you should have NO resistance readings no matter what, when the Key Switch, PTO Switch, or Brake Switch is engaged. IF you do, then start isolating until you find the short.
Next, testing the solenoid itself. I do not know the exact specification on the solenoid coil, only an educated guess. IF you have from the small terminal to ground, say 200 to 2000 ohms, the solenoid coil is probably OK. If it is over 2000 ohms, I would venture to say, the coil is toast. IF you have under 100 ohms....then this coil is shorted.
Do the testing and let is know.
