MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
7. COMPRESSOR RUNNING SLOW
Step 1. Check for low line voltage, or a defective motor starter heater.
Tighten loose terminals. If still running slow, notify Direct Support Maintenance.
Step 2. Check for leaking or maladjusted pilot unloader valve. Tighten leaking
fittings. Adjust pilot valve (para 3-9).
8. LIGHTS FLICKER WHEN COMPRESSOR RUNS.
Check terminals of motor.
If bad connections cannot-be rectified, notify Direct Support Maintenance.
Section VI. MAINTENANCE OF THE AIR COMPRESSOR
4-7. General
(4) Lift belts off the pulleys.
a. Motor. The motor is a 115/230 vac, single phrase,
b Cleaning and Inspection. Cleansed inspect the
60 hertz, induction motor, with initial connections for 115
belts as described in paragraph 3-7. Replace defective
vac.
belts.
b. V-Belts. The V-belt drive of the air compressor
c Installation.
consists of a matched pair of belts, and pulleys of a size
NOTE
designed for changing the motor speed of 1,750 rpm to a
Never pry new belts over edges of
compressor speed of 610 rpm.
pulley grooves. Be sure motor has
c Air Compressor. The air compressor is a two
been moved toward compressor so
stage, two cylinder compressor mounted on top of the air
that belts fit easily over the pulleys.
receiver. It is air cooled, by an intercooler between 1st
(1) Glean grooves in belt pulleys to be sure no
and 2nd stage cylinders, and an aftercooler between 2nd
oil or dust remains to damage new belts.
stage and the receiver. It has an unloader and pilot valve
to relieve internal pressure when the compressor is
(2) Place belts in their proper grooves, then
stopped. There is a breather tube between compressor
move motor away from compressor until belts are
frame and the inlet filter (inboard side). This connection
nominally tight. Tighten mounting nuts.
permits pulsations, created by the reciprocating action of
(3) Visually check bottom line of belts for a
the pistons, to be vented to the atmosphere. This
slight droop between pulley centers. If this droop is there,
eliminates any pressure build up within the frame.
belts should be in adjustment.
d Pilot Valve. When the pilot valve plate is
(4) If no droop is seen, the belts may be too
unseated by action of the centrifugal unloader, it permits
tight. Adjust by measurement and scale method described
pressure to bleed from the compressor and discharge
in paragraph 3-7 above.
line. The cylinders and the intercooler are also relieved of
all pressure while the compressor is stopped.
(5) When belts are adjusted, reinstall the front
belt guard (pare 3-5).
e Inlet Filter. The inlet filter cleans the air entering
the first stage cylinder. Frequent cleaning, the time period
(6) Unlock and turn on power at source.
depending on environment, is necessary to insure
4-10. Air Compressor Replacement
capacity output of the compressor.
a. Inspection. Inspect the air compressor as
4-8. Motor Removal and Installation
described in paragraph 3-8.
motor. Replace nuts on capscrews lightly for safekeeping.
b Removal
b Installation. Remove nuts from capscrews that
(1) Turn power off at source and lock it out.
were put there for safekeeping, then refer to figure 3-2
(2) Remove belt guard (pare 3-5), belts (pare
and install motor by reversing the removal procedure.
4-9), then close air line shutoff valve (fig. 1-1) and
4-9. V-Belt (Matched Pair) Replacement
remove the service line. Disconnect aftercooler from
a Removal
check valve in the air receiver.
(1) Turn off compressor power at source, and
(3) Remove 4 capscrews (2, fig. 4-2),
lock it out.
lockwashers (3) and air line hose support (4).
(2) Remove front belt guard (pare 3-5).
(3) Loosen nuts on motor mounting capscrews
motor toward the compressor.
4-3
