HYDRAULICS 1.47 Fan reverse valve (72) (From Machine S/No.51200472 only) The fan reverse valve is fitted between the hydraulic tank (1) , the cooling fan motor (7) and the parking brake valve (71) . The valve is manually operated from a switch in the operators cab and reverses the direction of rotation of the engine cooling fan. This enables debris that is blocking the radiator to be blown clear to restore correct cooling. The valve is supplied with hydraulic fluid from the auxiliary hydraulic pump (6) and has a solenoid operated valve, servo valve, pressure relief valve and a temperature operated switch.
In normal operating conditions, the hydraulic fluid supply from the auxiliary pump (6) is directed by the solenoid valve to the fan motor (7) . The return fluid is directed by the solenoid valve, through the oil cooler (73) to the hydraulic tank (1) . If the radiator becomes blocked, the temperature of the hydraulic fluid increases. When the fluid temperature reaches 100 °C, the temperature switch is operated. This illuminates a warning light in the operators cab. When the operator holds down the cab selector switch, the solenoid valve operates to reverse the flow of hydraulic fluid to the fan motor, reversing the direction of fan rotation.
A connection from the fan reverse valve supplies operating fluid to the parking brake valve (71) . Specifications Pressure relief valve 140 bar (2030 psi) max Temperature switch 100 °C Solenoid voltage 12V DC Key to Fan Reverse Valve 1. Solenoid operated valve 2. Non-return valves 3. Servo valve 4. Pressure relief valve 5. Temperature switch A Return from fan motor (7) B Supply to fan motor (7) M Temperature switch T Return to hydraulic tank (1) P1 Oil supply from auxiliary pump (6) P2 Supply to Parking brake valve (71)