Western Star 47X 2020, Maintenance Manual

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3. Inspect the air dryer for external damage, and
check that the unit is tightly mounted on the
frame. If the air dryer mounting is loose, repair it.
4. Turn on the ignition switch, but do not start the
engine.
5. Disconnect the harness connector from the air
dryer.
6. Connect a voltmeter to circuit 94 on the air dry-
er’s harness connector and to a body ground
point. Check for battery voltage. If voltage is not
found, check and repair the open or short to
ground in wire 94.
7. Connect a voltmeter between the two terminals
on the air dryer’s harness connector. If voltage is
not found, repair the open in the ground circuit
wiring.
8. Use an ohmmeter to check resistance between
the terminals on the end cover. See
Fig. 4 . The
end cover contains the heater/thermostat. If the
heater/thermostat is between 40 and 90°F (5 and
32°C), the heater/thermostat measured resis-
tance will be infinite ohms. If the measured resis-
tance is less than infinity, replace the
heater/thermostat.
9. Remove the heater/thermostat assembly and
place it in a freezer for about five minutes to cool
it below 40°F (5°C). Remove the cold
heater/thermostat assembly and check resis-
tance between the heater/thermostat terminals.
Resistance should be 1.5 to 3.0 ohms. As the
temperature of the heater/thermostat assembly
increases, the ohm reading will increase. When
the temperature goes above 45°F (7°C) mea-
sured resistance should be infinite ohms. If the
heater/thermostat does not operate as outlined,
replace it. If it does operate as outlined, install it.
42–04 Alcohol Evaporator
Cleaning and Inspection
Maintenance is required during both the freeze sea-
son and the off season to keep the alcohol evapora-
tor in good working order.
Off Season
During the off season, drain the unit of alcohol. At
regular engine service intervals, open the drain cock
to remove moisture from the alcohol evaporator. Be-
fore reactivating the evaporator for the next freeze
season, drain, disassemble, inspect, and steam-
clean the unit of any sludge that may have accumu-
lated. It is advisable to replace any rubber parts
when assembling the alcohol evaporator. Perform
this service just before the freeze season.
Freeze Season Reactivation
1. Park the vehicle on a level surface and apply the
parking brakes. Shut down the engine. Chock
the tires.
2. Remove the filler cap, and check the cap tet-
raseal.
3. Remove the capscrews and reservoir from the
cover.
4. Remove the cover tetraseal.
5. Drain the air tank, and disconnect the line from
the evaporator outlet. Remove the check-valve
retainer, spring, and disc.
6. Install the disc, spring, and check-valve retainer,
and connect the line to the evaporator outlet.
f421384 10/07/2016
1
2
1. End Cover Assembly
2. Heater/Thermostat Terminals
Fig. 4, End Cover Terminals Location
Brakes
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47X and 49X Maintenance Manual, August 2020
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