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| Illustration 1 | g01020016 |
Schematic for the Reversing Fan System (1) Reversing valve. (2) Solenoid valve (reversing valve). (3) Check valve. (4) Relief valve. (5) Stem. (6) Makeup valve. (7) Stem. (8) Solenoid valve (hydraulic fan). (9) Reversing motor. (X) Port for standard direction. (Y) Port for reverse direction. (10) Check valve (hydraulic oil cooler bypass). (11) Hydraulic oil cooler. (12) Crossover relief valves. (13) Pump control valve. (14) Hydraulic fan pump. (15) Hydraulic tank. (16) Screen group. (17) Sensor (hydraulic oil). (18) Sensor (Air intake manifold). (19) Sensor (transmission oil). (20) Sensor (engine coolant). (21) Fan override switch (cab panel). (22) Engine ECM. | |
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| Illustration 2 | g01019981 |
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| Illustration 3 | g01020135 |
Hydraulic fan pump (14) is mounted to the front housing of the engine on the right side of the machine. Hydraulic fan pump (14) draws oil from hydraulic oil tank (15) through the inlet of the fan pump. Pump supply oil from hydraulic fan pump (14) flows into the inlet of reversing valve (1) through hose (B). Then, the hydraulic oil flows through reversing valve (1) to hydraulic motor (9). The fan blades rotate. Hydraulic fan motor (9) is located at the rear of the machine between the radiator and the engine. The return oil flows from hydraulic motor (9) through reversing valve (1), and through hose (A). Return oil that is flowing through hose (A) will flow through oil cooler (11), and into hydraulic tank (15). The rotation of the fan forces cooling air to flow through the cooling package. The reversing fan also forces a reverse flow of cooling air through the cooling package.
When the engine is first started and the hydraulic oil is cold, the return oil from the piston motor can not easily flow through hydraulic oil cooler (11). The oil pressure will increase in the hydraulic oil cooler. The check valve (hydraulic oil cooler bypass) (10) will open. Check valve (10) limits the maximum oil pressure in hydraulic oil cooler (11) to 450 ± 55 kPa (65 ± 8 psi). Case drain oil from hydraulic fan pump (15) and the case drain from piston motor (9) flow through a hydraulic oil line to hydraulic oil tank (16). The oil from the case drain is filtered through a screen in hydraulic tank (15) .
When the temperature of the oil increases, the pressure of the oil decreases. The force of the spring in the check valve (hydraulic oil cooler bypass) (10) is greater than the force of the oil pressure that is acting on the spring. This allows the check valve (10) to close. The hydraulic oil flows through hydraulic oil cooler (12), and then into hydraulic tank (15) .
The hydraulic fan system controls the speed of the fan. The fan speed is controlled by four temperature sensors (17, 18, 19, 20). Sensors (17, 18, 19, 20) send data to engine ECM (22). Engine ECM (22) will interpret the data from the four sensors (17, 18, 19, 20). Then, engine ECM (22) sends a change in current to the solenoid valve (demand fan) (8). A reduction in current from engine ECM (22) will increase the flow of pump supply oil from hydraulic fan pump (15) to the hydraulic fan motor (9). An increase in current from engine ECM (22) will decrease the flow of pump supply oil from hydraulic fan pump (14) to the hydraulic fan motor (9) .
Reference: For information about the hydraulic fan pump, refer to the Service Manual module Systems Operation, "Piston Pump (Hydraulic Fan)" for the machine that is being serviced.
Reference: For information about the hydraulic fan motor, refer to the Service Manual module Systems Operation, "Piston Motor (Hydraulic Fan)" for the machine that is being serviced.
Reference: For information about adjusting the speed of the hydraulic fan system, refer to the Service Manual module Testing and Adjusting, "Hydraulic Fan Speed - Test and Adjust" for the machine that is being serviced.
In a machine that is equipped with a reversing fan system, fan motor (9) will rotate in both directions. The direction of the fan motor will be controlled by solenoid valve (2). If solenoid valve (2) is de-energized,the hydraulic fan motor will rotate in the standard direction. The flow of oil into reversing valve (1) will open check valve (3) and flow through stem (5). Then, the pump supply oil flows into port (X) of hydraulic motor (9) and hydraulic motor (8) rotates. As hydraulic motor (9) rotates, the return oil flows out of the hydraulic motor through port (Y), through stem (7), through hydraulic oil cooler (11), and into hydraulic tank (15) .
In the reversing valve (1), relief valve (4) regulates the pressure of the pump supply oil. Crossover relief valves (12) are installed in the valve in order to relieve any outside forces on the hydraulic fan system. The pressure in either of the passages that are flowing into the motor can rise suddenly if the fan blades are affected by an external force. In this case, the force on the crossover relief valve will open the respective relief valve and the oil will flow back to the hydraulic tank.
In the reversing valve (1), check valve (6) is installed for a makeup valve. The makeup valve eliminates cavitation of the fan motor (9) during reduced oil flow. When check valve (6) is open, the return oil will flow back through makeup valve (6). This condition happens when the fan slows and/or the fan stops. When the hydraulic fan pump slows down, the supply of oil to fan motor (9) is reduced. Fan motor (8) will continue to rotate because the resistance of the air that is being pushed through the radiator is not strong enough to stop the fan blade from turning fan motor (8). The force of the oil will override the spring in check valve (6). Check valve (6) will open and the return oil re-enters the fan motor through stem (5).
The hydraulic fan system rotates the fan blades in the standard direction for 20 minutes. After engine ECM (22) has timed out, solenoid valve (2) will receive current from engine ECM (22). Solenoid valve (2) will be energized. Then, the fan motor will rotate in the opposite direction for 25 seconds. After engine ECM (22) times out for the 25 seconds, the rotation of the fan motor changes to the standard direction. Illustration 4 shows the movement of solenoid valve (2) and the stems (5, 7) in reversing valve (1).
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| Illustration 4 | g01019972 |
Shifted Reversing Valve (1) Reversing valve. (2) Solenoid valve (reversing valve). (3) Check valve. (4) Relief valve. (5) Stem. (6) Makeup valve. (7) Stem. (8) Solenoid valve (hydraulic fan). (9) Reversing motor. (X) Port for standard direction. (Y) Port for reverse direction. (10) Check valve (hydraulic oil cooler bypass). (11) Hydraulic oil cooler. (12) Crossover relief valves. (13) Pump control valve. (14) Hydraulic fan pump. (15) Hydraulic tank. (16) Screen group. (17) Sensor (hydraulic oil). (18) Sensor (Air intake manifold). (19) Sensor (transmission oil). (20) Sensor (engine coolant). (21) Fan override switch (cab panel). (22) Engine ECM. | |
After 20 minutes of standard rotation, solenoid valve (2) is energized and the solenoid valve shifts to the right. Pilot oil is directed to the ends of the stem (5) and stem (7). Stem (5) and stem (7) will shift to the right. The path of oil will be changed. The pump supply oil from stem (5) now flows to port (Y) for the reverse direction of hydraulic fan motor (9). Return oil from port (X) of hydraulic motor (9) flows through stem (7) and to the hydraulic tank. Hydraulic fan motor (9) will rotate in the reverse direction for 25 seconds. After 25 seconds, the current from engine ECM (22) is interrupted and solenoid (2) is de-energized. The pilot oil to stem (5) and to stem (7) is blocked. Then, the springs in the stems (5, 7) shift stems (5, 7) to the left. Pump supply oil flows to port (X) for the standard direction and hydraulic fan motor (9) rotates in the standard direction for 20 minutes.
Operator Override
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| Illustration 5 | g01020209 |
Dash Panel
(21) Fan override switch.
When the operator determines that the fan motor should be reversed, fan override switch (21) can be momentarily activated. When fan override switch (21) is momentarily activated, a signal is sent to engine ECM (22). Engine ECM (22) sends current to solenoid valve (2) and the solenoid valve is energized. Solenoid valve (2) sends pilot oil to stems (5) and stem (7). Stems (5, 7) shift to the right and pump supply oil is sent to port (Y) on the hydraulic fan motor. The rotation of the fan motor will be reversed for 25 seconds. At that time, the current to solenoid valve (2) is interrupted and solenoid (2) is de-energized. Stems (5, 7) shift to the left. Pilot supply oil will be sent to port (X) for the standard direction. Hydraulic fan motor (9) rotates in the standard direction for 20 minutes or the operator activates fan override switch (21). Illustration 5 shows the location of the fan override switch on the panel.