2000 LEXUS GS400 check engine

AC0W7±02
I02352
Sight Glass
± AIR CONDITIONINGAIR CONDITIONING SYSTEM
AC±3
2688 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
ON±VEHICLE INSPECTION
1. INSPECT REFRIGERANT VOLUME
Observe the sight glass on the liquid tube.
Test conditions:

Running engine at 1,500 rpm

Blower speed control switch at ºHIº position

A/C switch ON

Temperature control dial at ºCOOLº position

Fully open the doors
ItemSymptomAmount of refrigerantRemedy
1Bubbles present in sight glassInsufficient*
(1) Check for gas leakage with gas leak de-
tector and repair if necessary
(2) Add refrigerant until bubbles disappear
2No bubbles present in sight glassNone, sufficient or too muchRefer item 3 and 4
3No temperature difference between com-
pressor inlet and outletEmpty or nearly empty
(1) Check for gas leakage with gas leak de-
tector and repair if necessary
(2) Add refrigerant until bubbles disappear
4Temperature between compressor inlet and
outlet is noticeably differentCorrect or too muchRefer to items 5 and 6
5Immediately after air conditioning is turned
off, refrigerant in sight glass stays clearToo much
(1) Discharge refrigerant
(2) Evacuate air and charge proper amount
of purified refrigerant
6When air conditioning is turned off, refriger-
ant foams and then stays clearCorrect±
*: Bubbles in the sight glass with ambient temperatures higher than usual can be considered normal if cooling
is sufficient.

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 CONDITIONINGAIR CONDITIONING SYSTEM
AC±7
2692 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
(6) Refrigerant overcharged or insufficient cooling of
condenser
Symptom seen in
refrigeration systemProbable causeDiagnosisRemedy

Pressure too high on both low
and high pressure sides

No air bubbles seen through the
sight glass even when the engine
rpm is lowered
Unable to develop sufficient per-
formance due to excessive refrig-
eration system

Insufficient cooling of condenser
Excessive refrigerant in
cycle " refrigerant over charged

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 systemProbable causeDiagnosisRemedy

Pressure too high on both low
and high pressure sides

The low pressure piping hot to
touch

Bubbles seen in sight glass
Air entered in refrigeration system

Air present in refrigeration sys-
tem

Insufficient vacuum purging
(1) Check compressor oil to see if
it is dirty or insufficient
(2) Evacuate air and charge new
refrigerant

± AIR CONDITIONINGAIR CONDITIONING SYSTEM
AC±9
2694 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
3. INSPECT IDLE±UP SPEED
(a) Warm up engine
(b) Inspect idle±up speed when the these conditions are es-
tablished.
Test conditions:

Blower speed control switch at ºHIº position

Temperature control dial at ºCOOLº position

A/C switch ON

Put gear shift in neutral
GS300:
Magnetic clutch conditionIdle±up speed
Magnetic clutch not engaged700 ± 50 rpm
Magnetic clutch engaged800 ± 50 rpm
If idle speed is not as specified, check the idle control system.
GS400:
Magnetic clutch conditionIdle±up speed
Magnetic clutch not engaged750 ± 50 rpm
Magnetic clutch engaged800 ± 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.

Stop engine

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)

Repeat the test 2 or 3 times

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:

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

Expose the gas leak detector sensor under the drain
hose.

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.

I02376
GS300:
3
I02375
GS400:
3
± AIR CONDITIONINGCOMPRESSOR AND MAGNETIC CLUTCH
AC±35
2720 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
5. MAKE THESE VISUAL CHECKS:
(a) Leakage of grease from the clutch bearing.
(b) Signs of oil on the pressure plate or rotor.
6. INSPECT MAGNETIC CLUTCH BEARING FOR NOISE
(a) Start engine.
(b) Check for abnormal noise from the compressor when the
A/C switch is OFF.
If abnormal noise is being emitted, replace the rotor of magnetic
clutch.
7. INSPECT MAGNETIC CLUTCH OPERATION
(a) Disconnect the connector.
(b) Connect the positive (+) lead from the battery to terminal
3 and the negative (±) lead to the body ground.
(c) Check that the magnetic clutch is energized.
If operation is not as specified, replace the magnetic clutch.

± AIR CONDITIONINGCOMPRESSOR AND MAGNETIC CLUTCH
AC±45
2730 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
6. GS400:
INSTALL SUCTION HOSE
Install the suction hose with the bolt and nut.
Torque: 10 N´m (100 kgf´cm, 7 ft´lbf)
NOTICE:
Hose should be connected immediately after the caps have been removed.
HINT:
Lubricate 2 new O±rings with compressor oil and install them to the hose.
7. INSTALL DRIVE BELT
(See page AC±16)
8. INSPECT DRIVE BELT TENSION
(See page AC±14)
9. INSTALL ENGINE UNDER COVER
10. CONNECT NEGATIVE (±) TERMINAL CABLE TO BATTER
11. EVACUATE AIR FROM REFRIGERATION SYSTEM AND CHARGE SYSTEM WITH REFRIGERANT
Specified amount: 600 ± 50 g (21.16 ± 1.76 oz.)
12. INSPECT FOR LEAKAGE OF REFRIGERANT
Using a gas leak detector, check for leakage of refrigerant.
If there is leakage, check the tightening torque at the joints.
13. INSPECT A/C OPERATION

AC0X8±01
AC±58
± AIR CONDITIONINGEXPANSION VALVE
2743 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
EXPANSION VALVE
ON±VEHICLE INSPECTION
1. CHECK QUANTITY OF GAS DURING REFRIGERATION CYCLE
2. SET ON MANIFOLD GAUGE SET
(See page AC±17)
3. RUN ENGINE
Run the engine at 1,500 rpm for at least 5 minutes.
Then check that the high pressure reading is 1.37 ± 1.57 MPa (14 ± 16 kgf/cm
2, 199 ±228 psi).
4. CHECK EXPANSION VALVE
If the expansion valve is faulty, the low pressure reading will drop to 0 kPa (0 kgf/cm
2, 0 psi).

I03741
2 1
3
4
AC0XN±01
Z13470
Magnetic Clutch Control
Low Pressure Side
ON (Continuity)
181 kpa
(1.85 kgf´cm
2, 28 psi)
OFF (No Continuity)High Pressure Side
3,140 kpa
(32.0 kgf´cm2, 455 psi)
OFF (No Continuity)
Z13471
Cooling Fan Control
ON1,520 kpa
(15.5 kgf´cm
2, 220 psi)
(No Continuity) (Continuity)
OFF
1,230 kpa
(12.5 kgf´cm
2, 178 psi) AC±76
± AIR CONDITIONINGPRESSURE SWITCH
2761 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
PRESSURE SWITCH
ON±VEHICLE INSPECTION
1. SET ON MANIFOLD GAUGE SET
(See page AC±17)
2. DISCONNECT CONNECTOR FROM PRESSURE
SWITCH
3. RUN ENGINE AT APPROX. 1,500 RPM
4. Magnetic Clutch Control:
INSPECT PRESSURE SWITCH OPERATION
(a) Connect the positive (+) lead from the ohmmeter to termi-
nal 4 and the negative (±) lead to terminal 1.
(b) Check continuity between terminals when refrigerant
pressure is changed, as shown in the illustration.
If operation is not as specified, replace the pressure switch.
5. Cooling Fan Control:
INSPECT PRESSURE SWITCH OPERATION
(a) Connect the positive (+) lead from the ohmmeter to termi-
nal 2 and the negative (±) lead to terminal 3.
(b) Check continuity between terminals when refrigerant
pressure is changed, as shown in the illustration.
If operation is not as specified, replace the pressure switch.
6. STOP ENGINE AND SET OFF MANIFOLD GAUGE SET
7. CONNECT CONNECTOR TO PRESSURE SWITCH

AC0Y2±01
I03743
1 2 AC±80
± AIR CONDITIONINGCONDENSER FAN
2765 Author: Date:
2000 LEXUS GS300/GS400 (RM718U)
CONDENSER FAN
ON±VEHICLE INSPECTION
1. INSPECT CONDENSER FAN OPERATION
Inspect the fan operation, as shown in the chart below.
Test conditions:

Ignition switch ON

Blower speed control switch position ºHIº

Temperature control dial at ºMAX. COOLº

Install manifold gauge setº

A/C switch ON
ConditionFan operation (Fan speed)
Engine coolant temperature
91°C (196 °F) or belowRotate (Low speed)
Engine coolant temperature
100°C (212 °F) or aboveRotate (High speed)
Refrigerant pressure is less than
1,520 kPa (15.5 kgf´cm2, 220 psi)Rotate (Low speed)
Refrigerant pressure is 1,520 kPa
(15.5 kgf´cm2, 220 psi) or aboveRotate (High speed)
If operation is not as specified, proceed to the next inspection.
2. INSPECT CONDENSER FAN MOTOR OPERATION
(a) Disconnect the fan connector.
(b) Connect the positive (+) lead from the battery to terminal
2 and negative (±) lead to terminal 1 then check that motor
operations smoothly.

If operation is not as specified, replace the fan mo-
tor.

If operation is as specified, check the pressure
switch, cooling fan relays and engine coolant temp.
switch.