4
FIGURE 8
FAN PLATE
lateral movement of the fan plate relative to the edge of the
pulley or a scribed line in the dust shield.
CHECKING PROCEDURE
1. Park the vehicle on a level surface and block the wheels.
2. Shut off the engine and apply a minimum of 85 p.s.i. to
the fan clutch to disengage it. NOTE: If air brake system
pressure is above 85 p.s.i. and the engine is cool, the
FD-3
™
fan clutch will be disengaged. Disengagement is
confirmed by noting that the fan can be rotated freely by
hand. DO NOT PERFORM THIS CHECK WITH THE
ENGINE RUNNING.
3. With the engine off and the FD-3
™
fan clutch disengaged,
grasp the tip of one fan blade using only the thumb and
index finger. (Refer to Figure 8.) Using a moderate force,
rock the fan blade back and forth toward the radiator
and measure the total movement of the fan plate relative
to the edge of the pulley.
Replace or repair the fan clutch if the total movement of
the fan plate is 1/16" or greater.
ALTERNATE METHOD - using thumb and index finger,
pull the fan blade toward the engine with a moderate
force and scribe a line on the dust shield along the
edge of the fan plate. After scribing the lines, push the
fan blade toward the radiator and measure the distance
between the scribed line and the edge of the fan plate.
(Alternate method not illustrated.)
Replace or repair the fan clutch if the total movement of
the fan plate is 1/16" or greater.
LINE HAUL VEHICLES
Every 50,000 miles; 1,800 hours, or every six months,
whichever occurs first, perform the service checks outlined
in this manual.
CITY DELIVERY
Every 15,000 miles, 300 hours or two months whichever
occurs first, perform the service checks outlined in this
manual.
SERVICE CHECKS
Before performing the operational and leakage checks,
apply the vehicle parking brakes or chock the wheels.
OPERATIONAL
1. With the engine cold, the ignition off and at least 75 psi
air pressure in the brake system, note that the fan is
disengaged from the pulley and can be turned by hand.
If the fan can be turned, proceed to Step #2. If it cannot
be turned;
A. Drain all reservoirs and disconnect the air control
line leading to the fan clutch and apply at least 75
psi shop air pressure to the fan clutch.
B. If the fan cannot be turned, the clutch is defective
and must be repaired or replaced (see appropriate
section of this manual).
C. If the fan can now be turned; check the air lines
leading to and from the thermostatic control valve for
‘kinks’ or obstructions, and check the control valve
itself according to the manufacturer’s instructions.
2. After performing check #1, drain all air pressure from the
brake system. Note that the fan is now engaged and
cannot be turned by hand. If it cannot be turned, proceed
to test #3. If it can be turned, the clutch is defective and
must be repaired or replaced.
3. Check the operation of the thermostatic control valve by
running the engine up to operating temperature.
Note that the fan clutch engages when engine
temperature rises to normal or above and disengages
after fan cooling is accomplished. Normal engagement
time should not exceed two minutes. If engagement time
does not exceed two minutes, proceed to check #4. If
engagement time does exceed two minutes:
A. If this test is being performed for the first time after
installation of the fan clutch, recheck the setting of
the thermostatic control valve and compare it with
the setting of the engine coolant thermostat or in the
case of vehicles with radiator shutters, with the
setting of the shutter control. The fan clutch control
should always be 10°F higher than the highest setting.
DUST SHIELD
PULLEY
THE TOTAL CHANGE IN THIS
DIMENSION FROM ITS
NARROWEST TO WIDEST
MEASUREMENT SHOULD
NOT BE 1/16” OR GREATER
