TM 5-4310-277-14
(1) Clean the head unloader parts with cleaning
solvent, Federal Specification P-D-680, and dry
thoroughly.
(2) Inspect all parts for cracks, breaks, wear,
distortion, and other damage. Replace a damaged or
defective part.
d. Assembly and Installation, Head Unloaders.
(1) Prior to installation of head unloader in
manifold, the actuating fork must be positioned so
that it will enter two slots in the compressor intake
valve. Reassemble the head unloaders, (a) through
(f), below. Note the position of the slots in the
compressor intake valve and rotate the actuating
fork to corresponding position. When the head
unloader piston is in uppermost position, the fork
should protrude 1/16 inch (.16 cm) below the bottom
of the manifold.
in the manifold (10); install the claw (7).
(b) Install spring (6), washers (5) and nuts
(4).
(c) Install O-ring (3), position a gasket (2),
and install the body (1).
the manifold (9); install claw (6) and spring (5).
(e) Install washers (4) and nuts (3).
(f) Install O-ring (2) and body (1).
(2) Holding the piston return spring in position
on the actuating fork with one finger, place head
unloader manifold in position over compressor intake
valve. Install screws, drawing up on both sides a
little at a time to insure proper entry of manifold into
compressor valve well. To check for correct
positioning
of actuating fork, place blunt in-
strument in opening at top of cylinder body and push
down on piston. If correctly installed, piston will
move down and the spring will return it.
(3) Tighten manifold capscrews to 45 ft-lbs (6.22
kgm). Reconnect all tubing.
(4) Start the compressor. When 50 psi (3.5150
kg per sq cm) or more pressure has been developed in
the air receiver tank, check manifolds near valve
parts and tube connections for leaks with a soap
solution. When pressure reaches approximately 175
psi (12.3025 kg per sq cm), the pilot valve should
actuate the head unloader and the compressor should
run unloaded. When this occurs a distinct difference
exploded view.
in sound will be heard and the unloaded air can be
felt coming out of compressor air cleaner. Run the
c. Cleaning and Inspection, Head Unloaders.
compressor in the unloaded condition for 5 to 10
minutes while the tank pressure is observed. Ad-
Dry cleaning solvent, P-D-680, used to clean
justment of the actuating forks must be made if the
parts is potentially dangerous to personnel
compressor fails to unload completely.
and property. Avoid repeated and
(5) Bleed the air from the tank down to ap-
prolonged skin contact. Do not use near
proximately 145 psi (10.1935 kg per sq cm). The pilot
open flame or excessive heat. Flash point of
valve should actuate and the compressor should run
solvent is 100 F. (38C.) - 138 F. (59 C.).
