(3)
Shortage of refrigeration
– 44 –
Cause of defect
Disposition
(1) Wind does not come out much
(a) Evaporator coil is frosted.
(b) Defrost solenoid valve is operating.
(2) There is a chink in the refrigeration van,
which brings in outside air.
(3) A lot of bubbles can been seen in sight
glass and refrigerant is reducing.
(4) Condenser coil is stained.
(5) In case the said items (1), (2), (3) and (4)
are normal,
(a) Expansion valve is clogged.
(b) Expansion valve is opened too much.
(c) Compressor valve is broken.
(a) Change operating time of defrost timer. (Type L only)
(b) Operate manual defrosting.
(c) It is normal if defrost is operating, but if defrost electromagnetic valve
is operating during cooling operation, Check for it. (Type L only)
Check and repair so as to get rid of chink.
Check for gas leakage and supply refrigerant after repair.
Wash by water. However, be careful that fin will be crushed if rubbed by
hard brush
(a) Start engine by connecting a gauge manifold and confirm that
compressor is operating. Through on the high pressure side shows
rather low value, expansion valve, receiver dryer or dryer is clogged
if low pressure side shows lower value than the one shown on page
41.
1) Expansion valve is clogged because water is frozen at the outlet of
expansion valve. So stop operation once, and then after inside ice
being melted, turn compressor again thermostat cylinder in
floating condition. If pressure on low pressure side goes up much
high and after a while pressure lower than the one when operated
normally is shown, it is suspected that water is in the cycle. In case
low pressure gauge will not go up even if thermostat cylinder is
floated, it is suspected that expansion valve is stuck or gas leaks
from thermostat cylinder. (Replace)
2) In case water is in, receiver refrigerant and replace receiver dryer
or dryer. As to vacuumization, use "repeating vacuumization
method", and charge after removing water completely. Also if
receiver dryer or dryer is clogged, low pressure gauge shows lower
pressure than the one when operated normally. And in a extreme
case, tubing followed by receiver dryer or dryer will become
frosted all over. And also in case they are slightly clogged,
temperature differs before and after receiver dryer or dryer.
(Replace)
(b) In case pressure on low pressure side is high and compressor
generates frost at the same time, expansion valve opens too much,
which indicates that refrigerant goes into compressor as liquid
refrigerant. Check for floating of thermostat cylinder. It is suspected
that expansion valve is stuck.
(c) In case there is little difference of pressure between high and low
pressure, either compressor valve is broken or expansion valve
opens too much. As to excessive opening of valve, determine by (b)
above, and as defective compressor valve, check whether or not the
difference of pressure between high and low pressure is normal with
gauge manifold being connected. In case temperature of condenser
will hardly go up, it is suspected that compressor is not compressed.
(check and repair)
