Komatsu PC200-8M0, Shop Manual, Page: 1226 / 1254

100 Air conditioner
Troubleshooting with gauge pressure
80-100
68
PC200, 200LC, 220, 220LC-8M0
SEN06151-00
*1: If refrigerant leaks, compressor oil in the air conditioner circuit always leaks, too. So perform the check
mainly on pipe joints and dirty parts with oil.
*2:
k When replacing a cooling cycle part, see “Caution about refrigerant” and collect refrigerant. After
replacing it, fill up the air conditioner system with refrigerant again.
*3: Sight glass is on the air conditioner hose near condenser.
Indicated gauge
pressure
Cause Check method Remedy
Pressure is normal
Air conditioner cycle is operating normally.
If there is any trouble (cooling trouble), there is another cause.
High-pressure: Approx. 1.5 to 1.7 MPa {15 to 17 kg/cm
2
}
Low-pressure: Approx. 0.13 - 0.2 MPa {1.3 - 2.0 kg/cm
2
}
–
<Both high-pres-
sure and low-pres-
sure are too low>
Low-pressure gauge
reads vacuum
Insufficient refrigerant
Bubble can be seen through sight glass. *1,
*3
Collect refrigerant, then
fill up with proper quan-
tity of refrigerant again
*2
Clogging of receiver drier
There is a temperature difference between
inlet and outlet pipes of receiver drier.
Tank is frosty
Replace
*2
Clogging of expansion valve Expansion valve is frosted
Clean or replace
*2
Gas leakage at thermoprobe of expan-
sion valve
Low-pressure gauge reads vacuum
Replace
*2
Defective evaporator temperature sensor
or defective contact of sensor (coming off
of mounting clip)
Evaporator is frozen
Flow rate of refrigerant is reduced due to
freezing.
(At Cool Max. and HI speed of fan, later it
becomes not to cold.)
Repair or replace
Replace receiver drier
Collect refrigerant, then
fill up with proper quan-
tity of refrigerant again
*2
Clogged or crushed piping
Piping between receiver drier and com-
pressor is clogged or crushed.
If clogged completely, low-pressure gauge
reads vacuum
Clean or replace
*2
<Both high-pres-
sure and low-pres-
sure are too high>
Filling too much with refrigerant Connect gauge manifold
Collect refrigerant, then
fill up with proper quan-
tity of refrigerant again
*2
Defective cooling of condenser
Dirty condenser, clogging or crushing of
fins, or defective rotation of cooling fan
Clean, repair fins, or
repair or replace con-
denser
*2
Improper adjustment of expansion valve
(Valve is opened too wide)
Bubble can be seen through sight glass. *3
Replace
*2
Air in cycle parts Bubble can be seen through sight glass. *3
Evacuate and then fill up
with proper quantity of
refrigerant again
*2
<High-pressure is
too high and low-
pressure is too low>
Clogged or crushed piping between com-
pressor and condenser There is a remarkable temperature differ-
ence across clogged part
Clean inside of cycle or
replace
*2
<High-pressure is
too low and
low-pressure is too
high>
Defective compressor (Compression
trouble of compressor)
Both high-pressure and low-pressure are
balanced while compressor is in operation.
Compressor has seized and is extremely
hot.
Replace
*2