I have a Gravely ZT50 that has had issues starting before. I suspected a safety switch on the parking brake, but can not locate one. I can hear the pto engage and disengage when i pull the switch, I jumped the seat switch harness just to be sure that wasnt the problem...is there a limit switch somewhere on the parking brake?
SOURCE: Can malfunction of PTO or other safety switches prevent start up of mower
You didn't state the model or brand of tractor, but usually the way the cranking circuit work is, from the "S" terminal of the ignition switch, the circuit runs to the PTO switch, if it's in the OFF position, the circuit then runs to the pedal switch, if it's in the DOWN (or brake on) position it then runs to the solenoid. On other tractors, from the ignition switch, the circuit runs to the pedal switch first. (The seat switch isn't used in the cranking circuit).
Any switch can go bad, but I would more likely suspect the pedal switch or loose connection at either switch. (But it could actually be the PTO switch).
Try tracing the circuit from the "S" terminal of the ignition switch through the PTO or pedal switches to the starter solenoid. You may get lucky and find something obvious.
If you find nothing, try jumping across the pedal or the PTO switch (only two terminals are used in the cranking circuit, trace back to ignition switch for the incoming, outgoing is usually directly adjacent). Jumpering will take these out of the circuit and tell you if either is bad internally.
Lastly, there's always the possibility that the ignition switch is bad. (Doesn't happen all that often, but it's suspect as well). Jumper from "B" terminal to "S" terminal will take it out of the circuit.
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