Operating instructions

TM 11574A-OI
3-52
f. System noises.
Step Probable Cause Remedy
1 Piping vibration. Support piping as required, check for
plugged liquid line strainer.
If fault is not corrected proceed to step 2.
2 Expansion valve hissing. Add refrigerant, check for plugged liquid line
strainer.
If fault is not corrected proceed to step 3.
3 Compressor noisy. Check valve plates for valve noise, replace
compressor (worn bearings), check for
loose compressor hold down bolts.
If fault is not corrected proceed to step 4.
4 Insufficient compressor oil. Add oil.
g. Compressor loses oil.
Step Probable Cause Remedy
1 Leak in system. Repair leaks.
If fault is not corrected proceed to step 2.
2 Plugged or stuck compressor oil return check
valve.
Repair or replace.
If fault is not corrected proceed to step 3.
3 Oil trapping in line. Check piping for oil traps.
h. Frosted suction line.
Step Probable Cause Remedy
1 Expansion valve admitting excess refrigerant. Adjust expansion valve.