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 TM 55-1905-220-14-11
5-147. REFRIGERATOR/FREEZER - MAINTENANCE INSTRUCTIONS (Continued).
SERVICE (Cont)
(b) Broken suction valve leaf:
A broken suction valve leaf, on the compressor, which is enclosed within the sealed compressor body shell,
prevents the piston from compressing the refrigerant vapor to increase head pressure.
3. Short cycling.
Control out of adjustment: By visually inspecting the control settings, the range indicator should be on (43 ) for
F
refrigerator, and (+5 ) on freezers. The differential indicator should be on (7 for refrigerators, and (5 for freezers. If
F
)
)
the differential indicator is set lower than (7, (5 in freezers, the unit will short cycle. Adjust differential for proper cut-
)
)
out.
4. Unit does not shut off.
(a) Control out of adjustment:
Using a remote reading thermometer, place the sensing bulb on a shelf in the refrigerator. If the unit does not
cut-in at (43 ) a cut-out at (37 ), then visually inspect the control. If the range indicator is below (43 ) unit will not
F
F
F
shut off. Raise range indicator to cut-in at (43 ). If differential indicator is set higher than (7 unit will not shut off at
F
)
proper temperature. Reset to (7.
)
(b) Control defective: If range indicator is on (+43 ) and differential indicator is on (+6 ) turn range-knob
F
F
counterclockwise to top of range scale. If unit fails to start, replace defective control.
5. Compressor inefficient.
Turn unit off. Connect low side pressure gauge to suction service valve. Close high side (liquid line) service valve.
Start the unit and allow to run for 5 minutes. The pressure gauge should read approximately 27" vacuum. Turn unit off.
Pressure gauge should stay at 27" vacuum, then unit is efficient. If unit does not pull to deep vacuum, and/or fails to
keep vacuum during test, unit is inefficient.
6. Expansion valve stuck open.
A hot liquid line and frosting suction line are indications of expansion valve open too wide. Replace expansion valve.
5-1528
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