Lexus SC300 / Lexus SC400. Manual — part 35
No.
Gauge reading kPa (kgf/cm
2
, psi)
Condition
Probable cause
Remedy
LO: 1.5 – 2.0
(21 –28, 147 –196)
HI:
14.5 – 15.0
(206 –213, 1422 –1471)
Normal cooling
Normally functioning
system
During operation, pressure at low
pressure side sometimes becomes a
vacuum and sometimes normal.
Periodically cools
and then fails to
cool.
Moisture present in
refrigeration system.
(1). Replace receiver
(2). Remove moisture
in system through
repeatedly
evacuating air
Inspection of Refrigeration System with Manifold Gauge Set
This is a method in which the trouble is located by using a manifold gauge set. (See ”Installation of Manifold
Gauge Set” on page
) Read the manifold gauge pressure when the following conditions are established:
(a) Temperature at the air inlet with the switch set at RECIRC is 30–35
°
C (86–95
°
F).
(b) Engine running at 2,000 rpm.
(c) Blower fan speed control switch set at high speed.
(d) Temperature control switch set at max. cool side.
HINT: It should be noted that the gauge indications may vary slightly due to ambient temperature conditions.
NOTICE:
•
Always recover refrigerant before removing the parts in the refrigerant line and evacuating air.
•
Evacuate air and charge proper amount of purified refrigerant after installing the parts in the
refrigerant line.
AC–100
–
AIR CONDITIONING SYSTEM
Troubleshooting
No.
Gauge reading kPa (kgf/cm
2
, psi)
Condition
Probable cause
Remedy
Pressure low at both low and high
pressure sides
Pressure too high at both low and
high pressure sides
Insufficient cooling
Bubbles seen in
sight glass
Insufficient cooling
Frost on tubes from
receiver to
unit
Replace receiver
Insufficient refrigerant
(1)
Check for gas
leakage with gas
leak tester and
repair if
necessary
(2)
Add refrigerant
until bubbles
disappear
Refrigerant flow
obstructed by dirt in
receiver
Insufficient cooling
Insufficient cooling of
condenser
(1). Clean condenser
(2). Check fan motor
operation
(1).
Check amount of
refrigerant
If refrigerant is
overcharged
(2).
Recover refrigeran
t
(3). Evacuate air and
charge proper
amount of purified
refrigerant
Refrigerant
overcharged
(
1). Replace receiver
(2). Check compres-
sor oil to see if
dirty
Air present in system
Insufficient cooling
Frost in Large
amount of dew on
piping at low
pressure side
Expansion valve
improperly mounted,
heat sensing tube
defective
(Open too wide)
(1)
Check heat sensing
tube installation
condition
If (1) is normal
(2)
Check expansion
valve and replace
if defective
(3). Remove air in
system through
repeatedly
evacuating air
NOTICE:
•
Always recover refrigerant before removing the parts in the refrigerant line and evacuating air.
•
Evacuate air and charge proper amount of purified refrigerant after installing the parts in the
refrigerant line.
HINT at 6:
These gauge indication are for when the refrigeration system has been opened and the refrigerant charged
without evacuating air.
–
AIR CONDITIONING SYSTEM
Troubleshooting
AC–101
No.
Gauge reading kPa (kgf/cm2, psi)
Condition
Probable cause
Remedy
Vacuum indicated at low pressure
side, very low pressure indicated at
high pressure.
Pressure too high at low pressure
sides, pressure too low at high
pressure side.
Refrigerant does not
circulate
Does not cool
(Cools from time
to time in some
cases)
Frost or dew seen
on piping before
and after receiver
or expansion
valve
(1)
Check heat sensing
tube for gas
leakage and
replace expansion
If (1) is normal
(2)
Clean out dirt in
expansion valve by
blowing with air if
not able to remove
dirt replace
expansion valve
(3)
Replace receiver
Does not cool
Insufficient
compression
Repair or replace
compressor
NOTICE:
•
Always recover refrigerant before removing the parts in the refrigerant line and evacuating air.
•
Evacuate air and charge proper amount of purified refrigerant after installing the parts in the
refrigerant line.
AC–102
–
AIR CONDITIONING SYSTEM
Troubleshooting
REFRIGERANT VOLUME
INSPECTION OF REFRIGERANT
VOLUME
1.
RUN ENGINE AT IDLE SPEED
2. OPERATE A/C AT MAXIMUM COOLING FOR A FEW
MINUTES
3.
INSPECT AMOUNT OF REFRIGERANT
Observe the sight glass on the liquid tube.
Item
Symptom
Amount of refrigerant
Remedy
1
Bubbles present in sight glass
Insufficient*
(1) Check for gas leakage with
gas leak tester and repair
if necessary
(2) Add refrigerant until
bubbles disappear
2
No bubbles present in sight
glass
None, sufficient or too much
Refer to items 3 and 4
3
No temperature difference
between compressor inlet and
outlet
Empty or nearly empty
(1) Check for gas leakage with
gas leak tester and repair
if necessary
(2) Add refrigerant until
bubbles disappear
4
Temperature between
compressor inlet and outlet is
noticeably different
Proper or too much
Refer to items 5 and 6
5
Immediately after air conditioner
is turned off, refrigerant in sight
glass stays clear
Too much
(1) Recover refrigerant
(2) Evacuate air and charge
proper amount of
purified refrigerant
6
When air conditioner is turned
off, refrigerant foams and then
stay clear
Proper
–
*: Bubbles in the sight glass with ambient temperatures higher can be considered normal if cooling is sufficient.
REFRIGERANT CHARGE VOLUME
Specified amount: 950
±
50 g (33.44
±
1.76 oz)
–
AIR CONDITIONING SYSTEM
Refrigerant Volume
AC–103
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