BLADE & EDGE 4Z9365 - Caterpillar

Demand Fan LOW SPEED
Illustration 6 g03501403
(1) Pump (Fan, Brake, Hoist)
(2) Solenoid (demand fan speed)
(3) Valve (Diverter)
(4) Pressure port (fan drive)
(5) Motor (Fan drive)
(6) Valve (anti-cavitation)
(7) Cooler (hydraulic oil)
(8) Valve (thermal bypass)The schematic above shows the hydraulic system with the hoist being RAISED and the demand fan in the LOW SPEED condition, due to hydraulic oil and engine coolant being COLD.The HOIST RAISE command is sending a high load sensing signal to Fan/Brake/Hoist Pump (1). This command causes the pump to UPSTROKE, to provide the pressure and flow required to RAISE the dump body on the truck. But because the hydraulic oil and engine coolant temperatures are COLD, Fan Drive Motor (6) needs to turn at LOW SPEED. The high signal pressure from the Hoist Control Valve to the pump control valve causes the pressure and flow in the hydraulic system to INCREASE. This condition would cause the fan to speed up beyond the cooling demand, given the temperature inputs.To regulate the hydraulic demand fan to the correct speed, the Transmission ECM INCREASES the current to Fan Speed Solenoid