TM 9-2320-360-10
1-15. AIR SYSTEM
Major systems on HET Tractor which operate with air include service and parking brakes, rear
suspension system, and Central Tire Inflation System (CTIS). Other vehicle components which operate
with air include the transfer case and interaxle lockups, winch tensioners and kickouts, windshield
washer, and horns. Vales are installed to isolate air-operated components so operation o one does not
affect the operation of another.
The air system consists of an engine-driven air compressor (1), a purge reservoir (2), and five air
reservoirs (3, 4, 5, 6, and 7). Air is drawn from the engine air intake and routed to the air compressor (1).
Pressurized air flows from the air compressor (1) thru an aftercooler (7.1), a coalescing filter (7.2), and air
dryers (8 and 9) where the air is cooled and the moisture/oil is removed. From the air dryers, air goes to
the purge reservoir (2) and air reservoir (3). The purge reservoir (2) supplies the air to purge the air
dryers (8 and 9) and aftercooler (7.1) when required. Moisture not removed by the air dryers will
condense in air reservoir. System air pressure is 120-125 psi (827-862 kPa). The air pressure in
reservoir (3) is sensed and controls air compressor operation.
Reservoir (3) supplies air to reservoirs (4, 5, 6, and 7) and CTIS. Reservoirs (5, 6, and 7) are
interconnected and separated from reservoir (4) with check vales. Reservoirs (5, 6, and 7) supply air to
operate the CTIS, service and parking brakes on rear tridem axles, and rear suspension system. Air
pressure in reservoirs (5, 6, and 7) is indicted by the red needle on the AIR PRESS Gage (10). Reservoir
(4) supplies air to operate service brakes on front axle, parking brakes on rear tridem axles, transfer case
and interaxle lockups, winch tensioners and kickout, windshield washes, and horns. Air pressure in
reservoir (4) is indicated by the green needle on the AIR PRESS Gage (10). If air pressure system falls
below 60 psi (414 kPa), an audible alarm will sound and the LOW AIR Indicator will light.
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