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 

AC–15

) 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