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TEMPERATURE-SENSITIVE FLUID FAN DRIVE
Effective in January, 1963, all Detroit-built Imperial, Chrysler and Dodge 880 models with factory-installed air conditioning have a temperature-sensitive fluid fan drive.
All 1964 models with factory-installed air conditioning will be equipped with this new fan drive.
These units may be identified by a small thermal coil mounted externally on the front face of the unit.
The thermal coil senses the temperature of the air entering the engine compartment through the radiator core. In cold weather, and when the engine is initially started up in hot weather, fan speed is very low compared to the speeds provided by other fan drives. When engine cooling requirements increase, the coil actuates a slide valve within the unit to uncover an orifice and permit more fluid to enter the active chamber.
When the orifice is completely uncovered, fan speed will equal or exceed engine speed, from idle up to about 1600 engine r.p.m.
The orifice is not completely uncovered unless coolant temperature in the upper tank of the radiator is above 220°F.
TESTING AND SERVICING
This is a sealed unit, serviced as an assembly.
New units in stock should be stored with the coil down, or on edge, to avoid the possibility of viscous fluid seeping into the bearing and contaminating the bearing lubricant.
If fan speed is still low when engine coolant temperature, measured in the upper tank of the radiator, is above 220°F, the fan drive unit should be replaced.
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