Hydraulic Fan System; Thermovalve - Holiday Navigator 2003 Owner's Manual

The hydraulic fan drive system cools the radiator, charge air cooler,
hydraulic fluid cooler, transmission cooler and the dash air conditioning
condenser. The components of the hydraulic fan system are: hydraulic reservoir,
filter, pump, two hydraulic fan motors (ISM), one hydraulic fan motor (ISL)
hydraulic switching valve and thermovalve. Cooling fan speed is proportional
to engine speed and radiator temperature. When radiator temperature rises
above 185º F, the wax thermovalve slowly closes off the bypassing hydraulic
fluid from the switching valve. As radiator temperature rises, a spool valve
begins to move in the switching valve. The spool valve directs the pressurized
hydraulic fluid to the fan motors. The higher the radiator temperature, the
further the spool valve is moved in the switching valve, providing a higher
volume of pressurized hydraulic fluid to the fan motors. Fan motor speed is
increased to meet the demand for cooling. The action of the thermovalve is
designed to move the spool in the switching valve to ramp up fan motor speed.
This design saves horsepower and increases fuel mileage by precise control of
hydraulic fan motor speed. The fan motors will increase in speed when the
motorhome is ascending long hills or operating in high ambient temperatures.
It is normal for the fans to "roar" when they are operating. Fan motor speed
and engine RPM are approximately the same with the switching valve at full
engagement.
The wax filled thermovalve is mounted at the top of the radiator sensing
coolant temperature. The thermovalve controls the action of the switching
valve. When the radiator is cool, the hydraulic fluid is allowed to flow through
the inlet and outlet ports of the thermovalve and return to the hydraulic reservoir.
As the coolant temperature inside the radiator rises to approximately 185º F,
the wax inside the thermovalve begins to melt and expand. This begins to
restrict hydraulic fluid flow through the thermovalve. The restricted hydraulic
fluid pressure then begins to move the internal spool valve of the switching
valve. This process will continue until coolant temperature inside the radiator
reaches approximately 199º F. At this temperature hydraulic fluid flow through
the thermovalve is stopped, moving the spool valve to full open position.
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N A V I G A T O R 2 0 0 3
Chassis Information
Hydraulic
Fan System

Thermovalve

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