TM 5-3655-210-12
Malfunction
Test or Inspection
Corrective Action
circulate through the refrigeration system Check that
the refrigerant sight glass (1) is full of refrigerant,
indicating an adequate charge.
Step 2. Check head pressure being too high due to air in the
system.
Discharge old refrigerant to air, and recharge
system as follows:
a Install a discharge pressure gage in the
discharge service valve.
b. Connect a full freon cylinder to the gage
port (3, fig. 4-4), using a charging hose with
dehydrator, and a vacuum-pressure gage.
Before tightening the charging hose
c.
connection at the compressor, crack the
cylinder valve slightly to purge air from the
hose.
d Close the suction service valve (2) one
turn.
e. Start the compressor, and slowly admit
freon from the supply cylinder until the sight
glass appears full of refrigerant.
CAUTION
If the compressor pounds, or frost forms on the cylinder
head, throttle down the rate of the flow of refrigerant with
the freon cylinder valve.
Step 3. Check for refrigeration compressor switch being out
of adjustment. The compressor pressure switches (1
and 2, fig. 4-15).
Set the suction pressure switch (2) to open at
zero psi to shut off the engine or electric
motor. The low pressure suction switches
reset to allow operations to resume when the
Figure 4-14. Choke control levers.
suction pressure rises to 12 psi (.8436 kg per
sq cm). Set the discharge switches (high
Malfunction
pressure) (1) to open at 240 psi (16.872 kg
Test or Inspection
per sq cm) to stop the electric motor or
Corrective Action
gasoline engine. The high pressure switches
Step 2. Check for loose connection in tank alarm circuit.
close to resume operation when the pressure
Tighten all loose connections.
drops to 210 psi (14.763 kg per sq cm).
9.
Pressure Vessel Pressure Too High, Refrigeration
Adjust the switches to the correct settings as
Unit Operates In Short Cycles
indicated on the dial by using a screw driver
Step 1. Check head pressure being too high due to service
on the adjusting screw.
valves being partly closed.
10.
Pressure Vessel Pressure Too High, Refrigeration
Completely open all refrigeration system
Unit Operates Continuously.
service valves as follows:
Step 1. Check to see if belts or clutches are slipping.
Remove the caps and open the inlet line (6,
Adjust the belts or clutches as follows:
fig. 4-4) and outlet shut-off valve on the
a. Clutch adjustment.
receiver tank (7) to allow the refrigerant to
(1) Loosen the setscrew (11, fig. 4-16) in the
adjustment nut (12).
(2) Release the clutch as far as possible.
(3) Unscrew the adjusting nut (12) until the
clutch can easily be engaged.
(4) Turn the adjusting nut (12) clockwise as
far as possible by hand.
(5) Release the clutch and tighten the
adjusting nut 1/8 turn.
4-16
