How do you troubleshoot a John Deere 185 hydro tractor that kills when pto is engauged?

First, check the operatorpresenceswitch located under the seat. Check and see if the wire are broken or that the switch is working. If this switch is broken the circuit to the deck will be tripped once the pto is trying to be engaged. If that doesn't work, next check and see if you have a battery that is strong enough to keep the electromagnet working.