General Compressor Repair Techniques
27
BROWN OIL. Indicates copper plating caused by
moisture in the system. Air in the system or high
compressor temperatures can cause oxidation
which will turn the oil brown. Change the
compressor oil if the test indicates the oil is acidic
GRAY OR METALLIC OIL. Indicates the
presence of wear particles that contain aluminum.
This is usually caused by bearing wear or piston
scoring. The compressor should be disassembled
and inspected for worn or damaged components.
The oil and oil filter should be changed.
GREEN OIL. Green compressor oil indicates
there is water in the system and copper plating
may have occurred. The compressor should be
disassembled and the shaft seal, bearings, gears,
and rotors should be inspected. Parts with
significant copper plating should be replaced, the
oil separator should be replaced, and the oil and
oil filter should be changed.
A contaminated system will cause a failure if left
uncorrected. The contaminate in the system will
break down the refrigerant oil, causing excessive
bearing wear and scoring of parts within the
compressor. Copper plating and moisture will
affect the valve plate rings and break down the
refrigerant and affects the capacity of the unit.
Particles and bearing scale traveling with the
refrigerant will plug the driers and expansion
valves, causing erratic operation until the
condition is corrected. Flushing with refrigerant
or the use of suction filters and liquid line driers is
recommended whenever a contaminated system is
found. In some cases, the contaminated condition
can be corrected by changing oil, refrigerant and
drier. Use a recommended evacuation process
before the unit is placed in service. See TK 40229
“Clean-up of Refrigeration Systems with Thermo
King Compressors.”