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The Tempatrol fan viscous drive is a torque- and tem
perature-sensitive clutch unit that automatically in
creases or decreases fan speed to provide proper engine
cooling.
The Tempatrol fan viscous drive clutch is essentially a
silicone-fluid-filled coupling connecting the fan assem
bly to the fan/water pump pulley. The coupling allows
the fan to be driven in a normal manner at low engine
speeds while limiting the top speed of the fan to a pre
determined maximum level at higher engine speeds. A
bimetallic spring coil is located on the front face. This
spring coil reacts to the temperature of the radiator
discharge air and engages the drive clutch for higher fan
speed if the air temperature from the radiator rises
above a predetermined temperature. Until additional
engine cooling is necessary, the fan will remain at a
reduced rpm regardless of the engine speed. Only when
sufficient heat is present in the air flowing through the
radiator core to cause a reaction from the bimetallic coil
will the Tempatrol drive clutch engage and increase fan
speed to provide the necessary additional engine cooling.
Once maximum fan speed is attained, the fan will not
rotate faster regardless of increased engine speed. When
the necessary engine cooling has been accomplished and
the degree of heat in the air flowing through the radi
ator core has been reduced, the bimetallic coil again
reacts and the fan speed is reduced to the previous
disengaged speed.
Rigid fan blades are fastened by rivets. The fan is
mounted on an aluminum spacer to provide the proper
distance between the fan and radiator.
WARNING: Do not stand in direct line with the fan
when the engine is operating, particularly at speeds
above idle.
Cherokees, Wagoneers and Trucks equipped with air
conditioning (or heavy-duty cooling) are equipped with a
Tempatrol (viscous drive) fan assembly. Six-cylinder en
gines not equipped with air conditioning or heavy-duty
cooling have a rigid metal, four-bladed fan.
Fan blade assemblies are balanced within 0.25 in. oz.
and should not be altered in any way. Replace a dam
aged or bent fan. Do not attempt repair. Refer to the
Cooling System Components chart for fan applications.
CAUTION: Fans are designed to be compatible with
certain applications only. DO NOT attempt to increase
cooling capacity by installing a fan not intended for a
given engine. Fan or water pump damage and noise may
result.
Replacement—All Models
(1) Disconnect fan shroud from radiator, if
equipped.
(2) Remove fan attaching bolts.
(3) Remove fan, spacer and shroud.
COOLING SYSTEMS
1C-13
NOTE: If equipped with a Tempatrol fan assembly,
remove attaching nuts and remove fan and drive as a
unit.
(4) Position replacement fan, spacer and shroud, if
equipped.
(5) Install fan attaching bolts (or nuts) and tighten.
(6) Install shroud attaching screws and tighten, if
removed.
Tempatrol Fan Blade and Drive Unit Replacement
CAUTION: Six-cylinder engines with a serpentine
(single) drive belt have a reverse rotating water pump
and viscous (Tempatrol) fan drive assembly. The com
ponents are identified by the words "REVERSE"
stamped on the coverof the viscousdrive andinnerside
of thefan, and "REV" cast into the water pump body.
Do not install components that are intended for non-
serpentine drive belts.
The Tempatrol drive unit should be replaced if there is
an indication of a fluid leak, noise, or if roughness is
detected when turning by hand. If the drive cannot be
turned by hand, or if the leading edge of the fan can be
moved more than 1/4 inch (6.35 mm) front to rear,
replace the drive unit.
If it necessary to replace either the Tempatrol fan
blade unit or the drive unit separately, use the following
procedure.
(1) Remove fan shroud attaching screws.
(2) Remove nuts attaching fan assembly and pulley
to water pump. Remove drive belt.
(3) Move shroud rearward and remove fan
assembly.
CAUTION: To prevent silicone fluid from draining
intofan drive bearing and contaminating the lubricant,
do not place Tempatrolfan uniton work bench withrear
mounting flange facing downward.
(4) Remove bolts attaching fan blade unit to drive
unit.
(5) Attach replacement unit. Tighten bolts with 13
foot-pounds (18 N»m) torque.
(6) Install fan assembly and pulley on water pump.
Tighten nuts with 18 foot-pounds (24 N«m) torque.
NOTE: Ifa four-cylinder engine, thefan assembly and
pulley must be installed with the drive belt in position
on pulleys.
Tempatrol Fan Test
In an engine overheating situation, the Tempatrol
drive unit can be statically tested for proper operation
by observing movement of the bimetallic spring coil and
shaft. To test, disconnect end of bimetallic spring coil
from slot (fig. 1C-12) and rotate it counterclockwise un
til a stop is felt.
NOTE: Do not force beyond stop.
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