I have a 1986 John Deere Model 316 riding tractor. I have a problem with a safety switch somewhere that I cannot seem to locate. When I start the motor and try to engage the hydrostat or the pto, it dies. I have replaced the switch on the hydro control and cut the wires on the seat switch and twisted them togethor, but still have the same problem. If I keep the switch on the hydro stick engaged the tractor will go a head and run with the hydro engaged. Can anyone steer me in the right direction. I am told there is a third switch but cannot find out where. Thanks