TROUBLE DIAGNOSIS
MTC-107
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MTC
Revision: January 2005 2004 Quest
Low-pressure Side Sometimes Becomes Negative
Low-pressure Side Becomes Negative
Gauge indication Refrigerant cycle Probable cause Corrective action
Low-pressure side sometimes
becomes negative.
● Air conditioning system
does not function and does
not cyclically cool the com-
partment air.
● The system constantly func-
tions for a certain period of
time after compressor is
stopped and restarted.
Refrigerant does not dis-
charge cyclically.
↓
Moisture is frozen at expan-
sion valve outlet and inlet.
↓
Water is mixed with refriger-
ant.
● Drain water from refrigerant
or replace refrigerant.
● Replace liquid tank.
AC354A
Gauge indication Refrigerant cycle Probable cause Corrective action
Low-pressure side becomes nega-
tive.
Liquid tank or front/rear side of
expansion valve′s pipe is
frosted or dewed.
High-pressure side is closed
and refrigerant does not flow.
↓
Expansion valve or liquid tank
is frosted.
Leave the system at rest until
no frost is present. Start it
again to check whether or not
the malfunction is caused by
water or foreign particles.
● If water is the cause, initially
cooling is okay. Then the
water freezes causing a
blockage. Drain water from
refrigerant or replace refrig-
erant.
● If due to foreign particles,
remove expansion valve
and remove the particles
with dry and compressed air
(not shop air).
● If either of the above meth-
ods cannot correct the mal-
function, replace expansion
valve.
● Replace liquid tank.
● Check lubricant for contami-
nation.
AC362A
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