Lexus RX300 (MCU15). Manual - part 85

I01450

Condition: Insufficient cooling

I01393

Condition : Does not cool

AC–8

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AIR CONDITIONING

AIR CONDITIONING SYSTEM

LEXUS RX300   (RM785E)

(8)

Expansion valve improperly

Symptom seen in 

refrigeration system

Probable cause

Diagnosis

Remedy

S Pressure too high on both low

and high pressure sides

S Frost or large amount of dew on

piping on low pressure side

Trouble in expansion valve

S Excessive refrigerant in low

pressure piping 

S Expansion valve opened too

wide

Check expansion valve 

Replace if defective

(9)

Defective compression compressor

Symptom seen in 

refrigeration system

Probable cause

Diagnosis

Remedy

S Pressure too high on low and

high pressure sides

S Pressure too low on high pres-

sure side

Internal leak in compressor

S Compression defective

S Valve leaking or broken sliding

parts

Repair or replace compressor

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AIR CONDITIONING

AIR CONDITIONING SYSTEM

AC–9

LEXUS RX300   (RM785E)

3.

INSPECT IDLE–UP SPEED

(a)

Warm up engine.

(b)

Connect the tachometer.

(c)

Inspect idle–up speed when the these conditions are es-
tablished.

Test conditions:

S

Blower speed control switch at ”HI” position

S

Temperature control dial at ”COOL” position

S

A/C switch ON

S

Put gear shift in neutral

Magnetic clutch condition

Idle–up speed

Magnetic clutch not engaged

700 

± 50 rpm

Magnetic clutch engaged 

(at cooling fan running ”LO” mode)

700 

± 50 rpm

Magnetic clutch engaged 

(at cooling fan running ”HI” mode)

730 

± 50 rpm

If idle speed is not as specified, check the idle control system.
4.

INSPECT FOR LEAKAGE OF REFRIGERANT

(a)

Perform in these conditions.

S

Stop engine

S

Secure good ventilation (If the gas leak detector
may not react volatile gases which are not refriger-
ant, such as evaporated gasoline and exhaust gas)

S

Repeat the test 2 or 3 times

S

Make sure that there is some refrigerant remaining
in the refrigeration system.
When compressor is OFF: approx. 392 – 588 kPa
(4 – 6 kgf·cm

2

, 57 – 85 psi)

(b)

Bring the gas leak detector close to the drain hose before
performing the test.

HINT:

S

After the blower motor has stopped, leave the cooling for
more than 15 minutes.

S

Expose the gas leak detector sensor under the drain
hose.

S

When bring the gas leak detector close to the drain hose,
make sure that the gas leak detector does not react to the
volatile gases.

If such reaction is unavoidable, the vehicle must be lifted up.
(c)

If gas leak is not detected on the drain hose, remove the
blower resistor from the cooling unit. Then insert the gas
leak detector sensor into the unit and perform the test.

(d)

Disconnect the connector and leave the pressure switch
for approx. 20 minutes. Then bring the gas leak detector
close to the pressure switch and perform the test.

(e)

Bring the gas leak detector close to the refrigerant lines.

AC1MG–01

N13795

Quick Disconnect
Adapter

Charging

Service Valve

Hose

N13794

Vacuum Pump

Vacuum Pump Adapter

N13791

Low Pressure
Service Valve

Vacuum Pump Adapter

High Pressure
Service Valve

Manifold
Gauge
Set

AC–10

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AIR CONDITIONING

AIR CONDITIONING SYSTEM

LEXUS RX300   (RM785E)

EVACUATING

1.

CONNECT QUICK DISCONNECT ADAPTER TO
CHARGING HOSES

2.

REMOVE CAPS FROM SERVICE VALVES ON RE-
FRIGERANT LINES

3.

SET ON MANIFOLD GAUGE SET

(a)

Close both hand valves of manifold gauge set.

(b)

Connect the quick disconnect adapters to the service
valves.

4.

EVACUATE AIR FROM REFRIGERATION SYSTEM

(a)

Connect the vacuum pump adapter to the vacuum pump.

(b)

Connect the center hose of the manifold gauge set to the
vacuum pump adapter.

(c)

Open both the high and low hand valves and run the vacu-
um pump.

(d)

After 10 minutes or more, check that the low pressure
gauge indicates 750 mmHg (30 in. Hg) or more.

HINT:
If the reading is 750 mmHg (30 in. Hg) or more, close both hand
valves of manifold gauge set and stop the vacuum pump.
Check the system for leaks and repair if necessary.
(e)

Close both the high and low hand valves and stop the vac-
uum pump.

(f)

Leave the system in this condition for 5 minutes or more
and check that there is no gauge indicator.

AC1MH–01

N13793

Charging Cylinder

High Pressure

Service Valve

Low Pressure

Service Valve

Push

Air

N13792

Gas Leak

Detector

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AIR CONDITIONING

AIR CONDITIONING SYSTEM

AC–11

LEXUS RX300   (RM785E)

CHARGING

1.

INSTALL CHARGING CYLINDER

HINT:
When handling the charging cylinder, always follow the direc-
tions given in the instruction manual.
(a)

Charge the proper amount of refrigerant into the charging
cylinder.

(b)

Connect the center hose to the charging cylinder.

CAUTION:
Do not open both high and low hand valves of manifold
gauge set.
(c)

Open the valve of charging cylinder.

(d)

Press the valve core on the side of manifold gauge and
expel the air inside of the center hose.

2.

INSPECT REFRIGERATION SYSTEM FOR LEAKS

(a)

Open the high pressure hand valve and charge refriger-
ant.

(b)

When the low pressure gauge indicates 98 kPa 
(1 kgf/cm

2

, 14 psi) close the high pressure hand valve.

(c)

Using a gas leak detector, check the system for leakage.

If leak is found, repair the faulty component or connection.
CAUTION:
Use the refrigerant recovery/ recycling machine to recover
the refrigerant whenever replacing parts.