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 TM 55-1905-219-14-11
5-144. REFRIGERATOR/FREEZER - MAINTENANCE INSTRUCTIONS (Continued).
LOCATION
ITEM
ACTION
REMARKS
TEST AND ADJUSTMENTS (Cont)
5. Compressor.
a. Testing the compressor.
If for any reason the compressor is not pumping sufficient gas, it is obvious that poor performance is the result.
This can be caused by leaky valves. To determine whether the valves are leaking, test as follows:
b. Vacuum test.
(1) A compound gauge is installed at the suction service valve. Shut off the suction line after having started the
compressor. A hammering sound, coming from the cylinder head, indicates that an excessive amount of oil is being
pumped through the compressor. Oil is incompressible and its presence in the cylinder and passing through the valves
caused the hammering. The valves are designed to stand this abuse. It nevertheless is undesirable because the oil is
gradually be transferred to the condenser and receiver, which means that insufficient oil remains in the crankcase to
lubricate the compressor. As soon as the compressor starts to pump oil, the motor should be shut-off for a short period
of time, and then restarted and stopped until quiet operation of the compressor is secured.
(2) All during this time, the compound gauge should be given careful attention and when the compressor pumps a
24 inch to 26 inch vacuum or more, it is operating properly. When a 24 inch - 26 inch vacuum is reached, the motor
should be shut-off, and the compound gauge carefully watched. In event the loss of vacuum is pronounced, that is, the
back pressure readings advance to a pressure within a short period of time, it is a very good indication of a leaky
discharge valve.
REPLACE
6. Refrigerator/
Replace defective or damaged
Freezer
unit, if necessary.
5-1466
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