TOYOTA SUPRA 1995 Service Owner's Guide

(See page AC±26)
(See page IN±30).
Check voltage between terminals TAM and SG of A/C amplifier connector.
Check ambient temperature sensor.
Check harness and connector between A/C amplifier and ambient
temperature sensor (See page
IN±30).
Proceed to next circuit inspection shown on matrix
chart (See page AC±26). However, if the light is still
blinking, check and replace A/C amplifier.
Check and replace A/C amplifier.
Repair or replace harness or connector.
Replace ambient temperature sensor.
Remove A/C amplifier with connectors still con-
nected.
1. Turn ignition switch ON.
2. Measure voltage between terminal TAM of SG
of A/C amplifier connector at each temperature.
HINT: As the temperature increases, the voltage decreases
gradually.
Voltage:
at 25°C (77°F): 1.35 ~ 1.75 V
at 40°C (104°F): 0.85 ~ 1.25 V
1. Remove the clip and the sensor from the right
side inside the bumper reinforcement.
2. Disconnect ambient temperature sensor connec±
tor.
Check resistance between terminals 1 and 2 of ambi-
ent temperature sensor connector at each tempera-
ture.

Resistance:
at 25°C (77°F): 1.6 ~ 1.8 k

at 50°C (122°F): 0.5 ~ 0.7 k

HINT: As the temperature increases, the resistance
decreases gradually.
NOTICE:
When installing the ambient temperature sensor,
be sure to connect the sensor connector before
connecting the battery.
INSPECTION PROCEDURE
± AIR CONDITIONING SYSTEMTROUBLESHOOTINGAC±31

Blinking Light FOOT Evaporator Temperature Sensor Circuit
CIRCUIT DESCRIPTION
This sensor detects the temperature inside the cooling unit and sends the appropriate signals to the
A/C amplifier.
Diagnostic Sensor Check Detecting ConditionTrouble Area
Open or short in evaporator temperature sensor
circuit.
Evaporator temperature sensor

Harness or connector between evaporator
temperature sensor and A/C amplifier

A/C amplifier
AC±32± AIR CONDITIONING SYSTEMTROUBLESHOOTING

INSPECTION PROCEDURE
(See page AC±26).
(See page IN±30)
Check voltage between terminals TE and SG of A/C amplifier connector.
Check and replace A/C amplifier.
Repair or replace harness or connector.
Replace evaporator temperature sensor.
Check harness and connector between A/C amplifier and evaporator
temperature sensor (See page
IN±30).
Proceed to next circuit inspection shown on matrix
chart (See page AC±26). However, if the light is still
blinking, check and replace A/C amplifier.
Check evaporator temperature sensor.
Remove A/C amplifier with connectors still con-
nected.
1. Turn ignition switch ON.
2. Measure voltage between terminal TE of SG
of A/C amplifier connector at each temperature.
HINT: As the temperature increases, the voltage decreases
gradually.
Voltage:
at 0°C (32°F): 2.0 ~ 2.4 V
at 15°C (59°F): 1.4 ~ 1.8 V
Check resistance between terminals 1 and 2 of evapo-
rator temperature sensor connector at each tempera-
ture.

Resistance:
at 0°C (32°F): 4.5 ~ 5.2 k

at 15°C (59°F): 2.0 ~ 2.7 k

HINT: As the temperature increases, the resistance
decreases gradually.

Remove evaporator temperature sensor (See page
AC±106)
± AIR CONDITIONING SYSTEMTROUBLESHOOTINGAC±33

Blinking Light F D Engine Coolant Temperature Sensor Circuit
CIRCUIT DESCRIPTION
This sensor detects the coolant temperature and sends the appropriate signals to the A/C amplifier.
These signals are used for warm up control when the engine is cold.
Diagnostic Sensor Check Detecting ConditionTrouble Area
Open or short in engine coolant temperature sensor
circuit.
Engine coolant temperature sensor

Harness or connector between engine coolant
temperature sensor and A/C amplifier

A/C amplifier
AC±34± AIR CONDITIONING SYSTEMTROUBLESHOOTING

INSPECTION PROCEDURE
(See page AC±26).
(See page IN±30)
Check voltage between terminals TW and SG of A/C amplifier connector.
Proceed to next circuit inspection shown on matrix
chart (See page AC±26). However, if the light is still
blinking, check and replace A/C amplifier.
Check engine coolant temperature sensor.
Replace engine coolant temperature sensor.
Check harness and connector between A/C amplifier and engine coolant
temperature sensor (See page
IN±30).
Repair or replace harness or connector.
Check and replace A/C amplifier.
Remove A/C amplifier with connectors still con-
nected.
1. Turn ignition switch ON.
2. Measure voltage between terminal TW of SG
of A/C amplifier connector at each temperature.
HINT: As the temperature increases, the voltage decreases
gradually.
Voltage:
at 0°C (32°F): 2.8 ~ 3.2 V
at 40°C (104°F): 1.8 ~ 2.2 V
at 70°C (158°F): 1.3 ~ 1.5 V
1. Remove A/C unit (See page AC±80).
2. Remove engine coolant temperature sensor.
Measure resistance between terminals 1 and 2 of en-
gine coolant temperature sensor connector at each
temperature.

HINT: As the temperature increases, the resistance
decreases gradually.
Resistance:
at 0°C (32°F): Below 50 k

at 40°C (104°F): 2.4 ~ 2.8 k

at 100°C (212°F): Over 0.2 k

± AIR CONDITIONING SYSTEMTROUBLESHOOTINGAC±35

Blinking Light DEF Solar Sensor Circuit
CIRCUIT DESCRIPTION
A photo diode in the solar sensor detects solar radi±
ation and sends signals to the A/C amplifier.
Diagnostic Sensor Check Detecting ConditionTrouble Area

Solar sensor

Harness or connector between solar sensor and
A/C amplifier

A/C amplifierOpen or short in solar sensor circuit.
Please not that blinking of the LED for DEF is not
abnormal when the sensor is not receiving solar
radiation.
AC±36± AIR CONDITIONING SYSTEMTROUBLESHOOTING

(See page IN±30)
Check and replace A/C amplifier.
Repair or replace harness or connector.
Check harness and connector between A/C amplifier and solar sensor
(See page
IN±30).
Replace solar sensor.
Check solar sensor.
Proceed to next circuit inspection shown on matrix
chart (See page AC±26). However, if the light is still
blinking, check and replace A/C amplifier.
Check voltage between terminals S5 and TS of A/C amplifier connector.
1. Turn ignition switch ON.
2. Measure voltage between terminal S5 of TS
of A/C amplifier connector when the solar sensor
is subjected to an electric light, and when the sen±
sor is covered by a cloth.
HINT: As the inspection light is gradually moved away
from the sensor, the voltage increases.
HINT: As the electric light is moved gradually away from
the sensor, the resistance increases.
1. Remove glove compartment assembly.
2. Remove solar sensor.
1. Cover the sensor by a cloth.
2. Measure resistance between terminals 1 and 2 of
solar sensor connector.
1. Remove the cloth from the solar sensor and sub±
ject the sensor to electric light.
2. Measure resistance.
Remove A/C amplifier with connectors still con-
nected.
ConditionVoltage
Sensor covered by a cloth
Sensor subjected to electric light
0.8 ~ 4.3 V
Below 0.8 V
Connect positive (+) lead of ohmmeter to terminal 2
and negative (±) lead to terminal 1 of the solar sen-
sor.
Resistance: 8 (no continuity)
Resistance: Approx. 4k(continuity)
INSPECTION PROCEDURE
± AIR CONDITIONING SYSTEMTROUBLESHOOTINGAC±37

Blinking Light A C Compressor Lock Sensor Circuit
CIRCUIT DESCRIPTION
This sensor sends 1 pulse per engine revolution to the A/C amplifier. If the number ratio of the compres-
sor speed divided by the engine speed is smaller than a predetermined value, the A/C amplifier turns
the compressor off. And, the indicator flashes at about 1 second intervals.
Diagnostic Sensor Check Detecting ConditionTrouble Area

Compressor
Compressor drive belt

Compressor lock sensor

Harness and connector between compressor and
A/C amplifier

A/C amplifierAll conditions below are detected for 3 secs. or more
(a) Engine speed: 450 rpm or more
(b) Ratio between engine and compressor speed
deviates 20% or more in comparison to normal
operation.
AC±38± AIR CONDITIONING SYSTEMTROUBLESHOOTING

INSPECTION PROCEDURE
(See page AC±26).
(See page IN±30).
Repair or replace harness or connector.
Replace compressor lock sensor.
Check for open and short harness and connector between A/C amplifier
and room temperature sensor (See page
IN±30).
Check compressor lock sensor.
Check compressor.
Adjust drive belt tension or repair compressor.
Proceed to next circuit inspection shown on matrix
chart (See page AC±26). However, if the light is still
blinking, check and replace A/C amplifier.
Disconnect compressor lock sensor connector
Measure resistance between terminals 1 and 2 of
compressor lock sensor connector.
Resistance: at 20°C (68°F): 160 ~ 210

(1) Check compressor drive belt tension.
(2) Check the compressor does not lock during operation with engine started and blower
switch
and A/C switch ON.
± AIR CONDITIONING SYSTEMTROUBLESHOOTINGAC±39

Blinking Light FRS Pressure Switch Circuit
CIRCUIT DESCRIPTION
The pressure switch sends the appropriate signals to the A/C amplifier when the air conditioning refrig-
erant pressure drops too low or rises too high. When the A/C amplifier receives these signals, it outputs
signals via the ECM to switch OFF the compressor relay and turns the magnetic clutch OFF.
Diagnostic Sensor Check Detecting ConditionTrouble Area

Pressure switch

Harness or connector between pressure switch
and A/C amplifier

Refrigerant pipe line

A/C amplifierOpen in pressure sensor circuit
Abnormal refrigerant pressure
below 196 kPa (2.0 kgf/cm2, 28 psi)
over 3,140 kPa (32.0 kgf/cm2, 455 psi)
AC±40± AIR CONDITIONING SYSTEMTROUBLESHOOTING