AIR TRACTOR AT-502A, Maintenance Section

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Maintenance Page 46 Air Tractor, Inc.
March 14, 2018 AT-502A/502B/504
Example
A large system with no leak requires new compressor, suction hose and
drier.
Drain oil from old compressor = 3 oz
Oil remaining in old compressor = .5 oz ( see note below )
Oil lost from old suction hose = 1 oz (from table)
Oil remaining in old drier = 1 oz (from table)
Amount to be added 5.5 oz
Example
—If the new compressor contains 8 oz (240 cc) you must drain
2.5 oz so the total in the compressor is 5.5 oz.
Note: When draining the old compressor roughly .5oz will remain in the compressor as film
coating all internal surfaces
.
8. Common Causes of Compressor Failure
A. Compressor Overheated

Overheating is most often caused by loss of refrigerant charge. Cool suction side
refrigerant returning from the evaporator provides cooling for the compressor. Once the
refrigerant charge is lost there is no refrigerant entering the compressor, hence no
compressor cooling. Blockages in the system will also prevent cool refrigerant flow to the
compressor.
B. Compressor Contaminated
There are several types of contamination. The most
common types are:

Foreign material like metal chips, dirt and
desiccant. Resulting in broken internal
compressor components eventually locking up
the compressor

Moisture from improper evacuation or hose
permeation. Moisture will corrode internal parts
resulting in failure. Moisture will create higher
system pressures or freeze in the expansion
device and blocking refrigerant flow.

Air Conditioning system flush
Note: New compressors are
delivered with full oil charge. It will
be necessary to add or subtract
from the delivered oil amount so
the total in the compressor
equals
the amount to be added .