RAM 1500 Truck 2WD V6-3.9L VIN X (1999)
Fan Clutch: Description and Operation
Viscous Fan Drive-Gas Engines
Viscous Fan Drive-Diesel Engine
The thermal viscous fan drive is a silicone-fluid- filled coupling used to connect the fan blades to the water pump shaft. The coupling allows the fan to
be driven in a normal manner. This is done at low engine speeds while limiting the top speed of the fan to a predetermined maximum level at higher
engine speeds.
