948 / 1002
HVAC
38
REFRIGERATION CYCLE TROUBLESHOOTING
Sr. No.
POSSIBLE CAUSE
REMEDY
3
Entry of moisture in
the refrigerant cycle
Condition
Air conditioner alternately cools and
does not cool.
Symptoms in refrigerant cycle
• During operation, the pressure on the
low pressure side alternates between
vacuum and normal.
Cause
The moisture mixed in the refrigerant in
the refrigerating cycle freezes in the
expansion valve orifice, blocking the
cycle. After a time, the ice melts and
normal conditions return
Diagnosis
The drier is in an oversaturated condi-
tion.
The moisture in the refrigerating cycle
freezes the expansion valve orifice, im-
peding refrigerant circulation.
Countermeasures
Remove the moisture by
repeated evacuation.
Recharge new refrigerant to
the specified amount.
4
Refrigerant fails to
circulate
Condition
Air conditioner does not cool. Symp-
toms in refrigerant cycle
Pressure on the low pressure side is
vacuum
Pressure on the low pressure side is
vacuum low.
Frost or dew is formed on the piping at
the front and rear side of the receiver or
the expansion valve.
Cause
Moisture or dirt in the refrigerating cycle
freezes or sticks to the expansion valve
orifice, obstructing refrigerant flow.
Gas leaking from the heat sensitizing
tube of the expansion valve obstructs
refrigerant flow.
Diagnosis
Blocked expansion valve orifice.
Countermeasures
Allow to stand for some
time and then resume op-
eration to decide whether
the blockage is caused by
moisture or by dirt. If
caused by moisture; re-
move the moisture by
repeated, Recharge new re-
frigerant to the specified
amount.
If cased by dirt; remove the
expansion valve and blow
out the dirt with com-
pressed air. If unable to
remove the dirt, replace the
expansion valve. Evacuate
and charge new refrigerant
to the specified amount. If
caused by gas leaking from
heat sensitizing tube, re-
place the expansion valve.