down the engine. Separate the halves of the fan
solenoid connector. The fan clutch should en-
gage.
If the fan does not operate correctly, see Group
20 of the
Business Class
®
Trucks Service
Manual
for troubleshooting and repair proce-
dures.
8. With the air system charged to 120 psi (827
kPa), and with the fan solenoid connector halves
separated, check the fan clutch for audible air
leaks, using a suitable listening device.
9. If a leak is detected, remove the fan blade. Using
a soapy water solution, check the fan clutch at
the following locations to locate the source of the
leak. Install a new seal kit. See Group 20 of the
Business Class
®
Trucks Service Manual
for re-
pair procedures.
9.1 Check for a leak at the bleed hole on the
fan pilot. Air leakage means that the car-
tridge assembly (Fig. 6, Ref. 16) or face
seal (Ref. 17) is damaged.
9.2 Check for air leaks between the air cham-
ber and the piston friction disc. Air leak-
age means that the large O-ring (Ref. 14)
is damaged.
9.3 Check for air leaks around the safeguard
hole on the piston friction disc. Air leak-
age means the small O-ring (Ref. 18) is
damaged.
9.4 Check for air leaking from the System
Sentry
®
fuse. Leaking air means the
clutch has gotten so hot the lead alloy in
the fuse melted. This released the clutch
before the heat could damage the clutch
bearings. Before replacing the fuse, find
and repair the source of the heat.
10. If equipped with an override toggle switch on the
dash, check the fan clutch operation as follows:
10.1 Connect the halves of the fan solenoid
connector.
10.2 Turn the air conditioner off.
10.3 Start the engine and charge the air sys-
tem to 120 psi (827 kPa). Tests must be
performed with the engine temperature
below 205°F (96°C) for Caterpillar en-
gines, and below 200°F (93°C) for Cum-
mins and Detroit Diesel engines.
10.4 Set the toggle switch to the ON position;
the fan clutch should engage.
10.5 Apply the foot brake, and release the
parking brakes.
10.6 Set the toggle switch to the AUTO or OFF
position; the air should exhaust and the
fan clutch should disengage. Replace the
switch if necessary.
11. If the fan stays engaged at all times on a Detroit
Diesel engine, check the circuit breaker labeled
"engine fan."
Kysor K22RA Fan Clutch
1. Disconnect the electrical cables from the battery.
Drain all air from the air system. If equipped with
an air starter, drain the air starter reservoir.
WARNING
If the engine starts during this procedure, the fan
could cause personal injury. If the vehicle is
equipped with an air starter, be sure that the air
starter reservoir is drained.
2. Measure the distance from the back surface of
the fan clutch retaining plate to the forward-most
edge of the fan belt pulley. See Fig. 7, Ref. A.
3. Disconnect the line from the air inlet of the air
cylinder. Connect a shop air hose to the inlet.
4. Apply a minimum of 100 psi (690 kPa) air pres-
sure to the air cylinder—the bearing housing will
move backwards, disengaging the clutch. Again,
measure the distance from the back surface of
the retaining plate to the forward-most edge of
the fan belt pulley.
5. Compare the two measurements; if the difference
between the two measurements exceeds 0.150
inches (3.8 mm), the clutch lining is worn and
must be replaced. See Group 20 of the
Busi-
ness Class
®
Trucks Service Manual
for clutch
lining replacement instructions.
6. Release the air pressure, then disconnect the
shop hose from the air inlet of the air cylinder.
Connect the vehicle air hose to the inlet.
7. Connect the electrical cables to the battery.
Engine Cooling/Radiator 20
Business Class Trucks Maintenance Manual, August 2003 20/5
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