Monaco SIGNATURE 2001 series, Owner'S Manual

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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 Fahrenheit, the wax inside the thermovalve begins to
melt and expand. This begins to restrict hydraulic fluid flow through the ther-
movalve. 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
Fahrenheit. At this temperature hydraulic fluid flow through the thermovalve
is stopped, moving the spool valve to full open position.
NOTE: The ISM series engine has a piloted orifice at the inlet port
of the switching valve. This allows the fan motors to spin at a low
rpm, even when the radiator is cool. This is to keep the dash air
conditioning compressor at proper operating temperatures. It is
normal for the engine fans to spin when the engine is idling even at
cool radiator temperatures.
The switching valve is mounted to the fan motor. This valve controls
direction of high pressure hydraulic fluid flow. High pressure hydraulic fluid
comes from the hydraulic pump to the switching valve and is returned back
to the reservoir. Either the thermovalve or the electric override valve directs
the fluid to the spool in the switching valve. When the radiator is cool, pres-
surized hydraulic fluid will bypass the fan motors and return to the fluid
reservoir. As radiator temperature rises, the thermovalve signal is slowed or
stopped to the switching valve. High pressure fluid is then directed to the fan
motors, cooling the radiator.
Motorhomes equipped with an ISM engine have an electric over
hydraulic override control valve. The override valve is located at the lower
rear corner of the radiator package. This valve is a normally closed valve
which is plumbed parallel with the thermovalve. It performs the same
hydraulic signal function as the thermovalve, but is electrically controlled by
the ISM engine. The ISM engine monitors intake manifold temperature. The
Chassis Information
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S I G N A T U R E 1 0 • 3 0 2
Thermovalve
Switching Valve
Electric Override
(ISM engine)