PTO Circuit Function
To energize the PTO solenoid and allow safe operation of the PTO system.
PTO Circuit Operating Conditions
– Engine running
– Operator ON seat
– PTO switch ON
– Engine running
– Operator OFF seat
– Transmission in neutral
– Park brake engaged
– PTO switch ON (Rear PTO Only)
PTO Circuit Theory of Operation
Signals from the coolant temperature sensor and seven switches (neutral, seat, park brake, MBR, PTO, reverse pedal sense, and front hitch detection) are read by the control cluster.
Logic inside the cluster determines if the inputs meet the requirements for energizing the PTO solenoid in a safe manner. Any disallowed state immediately turns off the fuel shutoff solenoid and disables engine cranking.
The display panel PTO light glows when the PTO switch is ON. A shift lever selects which PTO output shafts engage. The REAR PTO ONLY position closes the contacts of the MBR (mid-both-rear) switch.
The seat switch must remain closed while the machine is in motion. However, the operator can leave the seat and operate the rear PTO when the transmission is in neutral and the park brake is locked. The mid PTO cannot be used while the operator is off-seat.
The RIO position of the PTO switch allows the operator to operate mid mount implement while the tractor is traveling in the reverse direction. This function must be selected before each time the tractor is placed in reverse.
To prevent shock loads when engaging the PTO, the control cluster first ramps up the current to the PTO solenoid over a two-second period. Current is then maintained at 1100 mA ±50 mA by using pulse width modulation at a frequency of 100~200 Hz.
The PTO solenoid de-energizes when any of these conditions occur:
– Key switch is OFF
– The PTO switch is OFF
– Electrical system measures < 9 or > 20 volts
– Solenoid current cannot be maintained for at least 4 seconds
– The temperature gauge enters the red zone (≥112 °C). Power remains off until the temperature drops below 98 °C and the PTO switch is cycled OFF and ON
– A disallowed off seat state is encountered