Komatsu PC88MR-10 Shop Manual page 1401

Indicated gauge pressure
Pressure is normal
<Pressure of both high-
pressure and low-
pressure lines are too
low>
Low-pressure line gauge
reads vacuum
<Pressure of both high-
pressure and low-
pressure lines are too
high>
PC88MR-10
Cause
Air conditioner cycle is operating normally.
If any problem (poor cooling) is recognized, the cause
is in other system.
Pressure of high-pressure line: Approx. 1.5 to -1.7
MPa {15 to 17 kg/cm 2 }
Pressure of low-pressure line: Approx. 0.13 to 0.2
MPa {1.3 to 2.0 kg/cm 2 }
Insufficient refrigerant
Clogging of receiver drier
Clogging of expansion
valve
Gas leakage at
thermoprobe of expansion
valve
Defective evaporator
temperature sensor or
defective contact of
sensor (coming off of
mounting clip)
Clogged or crushed piping
Filling of too much
refrigerant
Defective cooling of
condenser
Defective adjustment of
expansion valve
(Valve is excessively
opened.)
Air sucked in cooling
cycle parts
Troubleshooting with gauge pressure
Check method
Bubbles can be seen
through sight glass. *1, *3
Temperature difference is
recognized between inlet
and outlet pipes of
receiver drier.
Tank is frosty.
Expansion valve is frosty. Clean or replace *2
Low-pressure line gauge
reads vacuum.
Evaporator is frozen.
Flow rate of refrigerant is
reduced due to freezing.
(If air conditioner is set to
Cool Max. and HI fan
speed modes, later its
cooling performance
lowers.)
Piping between receiver
drier and compressor is
clogged or crushed.
If clogged completely, low-
pressure line gauge reads
vacuum
Connect gauge manifold.
Check condenser for dirt,
fins for clogging or
crushing, and cooling fan
for defective rotation.
Bubbles can be seen
through sight glass. *3
Bubbles can be seen
through sight glass. *3
80 Appendix
Remedy
Collect refrigerant, then fill
up with proper quantity of
refrigerant again. *2
Replace *2
Replace *2
Repair or replace
Replace receiver drier.
Collect refrigerant, then fill
up with proper quantity of
refrigerant again. *2
Clean or replace *2
Collect refrigerant, then fill
up with proper quantity of
refrigerant again. *2
Clean condenser, repair
fins, or repair or replace
cooling fan *2
Replace *2
Evacuate air from air
conditioner and then fill up
with proper quantity of
refrigerant again. *2
80-77