Method and apparatus for preventing the solenoid from being heated by an excitation current. When the hydraulic cylinder extends and retracts, the controller instructs the high driver to input an adjustable current to the solenoid to move the solenoid valve body to the connected position. The controller then instructs the high driver to input a steady current to the solenoid, keeping the valve in the on position. Adjustable current and steady current are pulse wave. The duty cycle of the steady current is less than the duty cycle of the adjustable current.