Lexus RX300 (MCU15). Service manual — part 84
I01386
AC–4
–
AIR CONDITIONING
AIR CONDITIONING SYSTEM
LEXUS RX300 (RM785E)
2.
INSPECT REFRIGERANT PRESSURE WITH MAN-
IFOLD GAUGE SET
This is a method in which the trouble is located by using a man-
ifold gauge set. Read the manifold gauge pressure when these
conditions are established.
Test conditions:
S
Temperature at the air inlet with the switch set at RECIRC
is 30 – 35
°C (86 – 95 °F)
S
Engine running at 2,000 rpm
S
Blower speed control switch at ”HI” position
S
Temperature control dial on ”COOL” position
HINT:
It should be noted that the gauge indications may vary slightly
due to ambient temperature conditions.
(1)
Normally functioning refrigeration system.
Gauge reading:
Low pressure side:
0.15 – 0.25 MPa (1.5 – 2.5 kgf/cm
2
)
High pressure side:
1.37 – 1.57 MPa (14 – 15 kgf/cm
2)
I01387
Condition : Periodically cools and then fails to cool
I01388
Condition: Insufficient cooling
–
AIR CONDITIONING
AIR CONDITIONING SYSTEM
AC–5
LEXUS RX300 (RM785E)
(2)
Moisture present in refrigeration system.
Symptom seen in
refrigeration system
Probable cause
Diagnosis
Remedy
During operation, pressure on low
pressure side sometimes become
a vacuum and sometime normal
Moisture entered in refrigeration
system freezes at expansion valve
orifice and temporarily stops cycle,
but normal state is restored after a
time when the ice melts
S Drier in oversaturated state
S Moisture in refrigeration system
freezes at expansion valve orifice
and blocks circulation of refriger-
ant
(1) Replace condenser
(2) Remove moisture in cycle
through repeatedly evacuating air
(3) Charge proper amount of new
refrigerant
(3)
Insufficient cooling
Symptom seen in
refrigeration system
Probable cause
Diagnosis
Remedy
S Pressure low on both low and
high pressure sides
S Bubbles seen in sight glass con-
tinuously
S Insufficient cooling performance
Gas leakage at some place in re-
frigeration system
S Insufficient refrigerant in system
S Refrigerant leaking
(1) Check for gas leakage with gas
leak detector and repair if neces-
sary
(2) Charge proper amount of re-
frigerant
(3) If indicated pressure value is
near 0 when connected to gauge,
create the vacuum after inspecting
and repairing the location of the
leak
I01389
Condition: Insufficient cooling
I01449
Condition: Does not cool (Cools from time to time in some cases)
AC–6
–
AIR CONDITIONING
AIR CONDITIONING SYSTEM
LEXUS RX300 (RM785E)
(4)
Poor circulation of refrigerant
Symptom seen in
refrigeration system
Probable cause
Diagnosis
Remedy
S Pressure low in both low and
high pressure sides
S Frost on tube from condenser to
unit
Refrigerant flow obstructed by dirt
in condenser
condenser clogged
Replace condenser
(5)
Refrigerant does not circulate
Symptom seen in
refrigeration system
Probable cause
Diagnosis
Remedy
S Vacuum indicated on low pres-
sure side, very low pressure indi-
cated on high pressure side
S Frost or dew seen on piping be-
fore and after condenser/ drier or
expansion valve
S Refrigerant flow obstructed by
moisture or dirt in refrigeration sys-
tem
S Refrigerant flow obstructed by
gas leakage from expansion valve
Refrigerant does not circulate
(1) Check expansion valve
(2) Clean out dirt in expansion
valve by blowing with air
(3) Replace condenser
(4) Evacuate air and charge new
refrigerant to proper amount
(5) For gas leakage from expan-
sion valve, replace expansion
valve
I01390
Condition: Insufficient cooling
I01392
Condition: Insufficient cooling
NOTE : These gauge indica-
tions are shown when the
refrigeration system has
been opened and the refrig-
erant charged without vacu-
um purging.
–
AIR CONDITIONING
AIR CONDITIONING SYSTEM
AC–7
LEXUS RX300 (RM785E)
(6)
Refrigerant overcharged or insufficient cooling of
condenser
Symptom seen in
refrigeration system
Probable cause
Diagnosis
Remedy
S Pressure too high on both low
and high pressure sides
S No air bubbles seen through the
sight glass even when the engine
rpm is lowered
S Unable to develop sufficient per-
formance due to excessive refrig-
eration system
S Insufficient cooling of condenser
S Excessive refrigerant in
cycle → refrigerant over charged
S Condenser cooling → condenser
fins clogged of condenser fan
faulty
(1) Clean condenser
(2) Check condenser fan motor
operation
(3) If (1) and (2) are in normal
state, check amount of refrigerant
Charge proper amount of refriger-
ant
(7)
Air present in refrigeration system
Symptom seen in
refrigeration system
Probable cause
Diagnosis
Remedy
S Pressure too high on both low
and high pressure sides
S The low pressure piping hot to
touch
S Bubbles seen in sight glass
Air entered in refrigeration system
S Air present in refrigeration sys-
tem
S Insufficient vacuum purging
(1) Check compressor oil to see if
it is dirty or insufficient
(2) Evacuate air and charge new
refrigerant
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