the john deere has 2 or 3 saftey switches, before buying, there is a simple test to see if thats the problem.. first off ... run a test lead from the neg side of the battery to the top of the starter.. it should turn over.. next clean the ground lead on the harness, this is located on the neg side of the battery connected to the frame.. clean the bolt and surrounding area.. the replace back as it was taken off.. it should fire up and run.. if not then go to the key switch.. turn it on, listen for the click of the solenoid, if you hear that.. then take a ohms meter and see how much power thats coming from the postive cable to the one side of the solenoid, it should be 12.65, with the key off.. turn the key to start, check to cable from the other side of the solenoid to the end of the cable attached to the starter. it should have the same output.. if it is a saftey switch, it will be located below the solenoid, that inter-lock switch works when you press down on the brake/clutch.. those are most common in going out.. but run the test that i set out above, before spending any money.. make sure you postive, and neg are hooked up on your post on the solenoid.. that is all I can you, unless you call me,