1995 TOYOTA SUPRA sensor

(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

Check voltage between terminal PSW of A/C amplifier and body ground.
Check pressure switch.

Repair or replace harness or connector.
Check and replace A/C amplifier.
Repair or replace harness or connector.
Check harness and connector between A/C amplifier and room
temperature sensor (See page IN±30).
Proceed to next circuit inspection shown on matrix
chart (See page AC±26).
Install the manifold gauge set.
The voltage changes with gas pressure, as shown
in the diagram below.
1. Turn ignition switch ON.
2. Check voltage between terminal PSW of A/C
amplifier connector and body ground when air
conditioning gas pressure is changed.
Disconnect pressure switch connector.
1. Turn ignition switch ON.
2. Check continuity between terminals 1 and 4 (2
and 1) of pressure switch when air conditioning
gas pressure is changed.
The continuity changes with gas pressure as
shown below
Low Pressure Cut Side
Low Pressure Cut SideReference:
High Pressure Cut Side
Reference:
High Pressure Cut Side
INSPECTION PROCEDURE
± AIR CONDITIONING SYSTEMTROUBLESHOOTINGAC±41

Blinking Light REC M2 Air Mix Damper Position Sensor Circuit
CIRCUIT DESCRIPTION
This sensor detects the position of the air mix
damper and sends the appropriate signals to the
A/C amplifier.
The position sensor is built into the air mix damp-
er control servo motor assembly.
Diagnostic Sensor Check Detecting ConditionTrouble Area

Air mix damper position sensor

Harness or connector between air mix
damper control servo motor assembly and
A/C amplifier

A/C amplifier
Light
REC
M2
Short to ground or power source circuit in air
mix damper position sensor circuit.
Air mix damper position sensor value does not
change even if A/C amplifier signals the air mix
damper control servo motor to operate.
AC±42± AIR CONDITIONING SYSTEMTROUBLESHOOTING

(See page IN±30).
Check voltage between terminals TP and SG of A/C amplifier connector.
Check air mix damper position sensor.
Check and replace A/C amplifier.
Check harness and connector between A/C amplifier and air mix
damper control servo motor assembly (See page IN±30).
Repair or replace harness or connector.
Replace air mix damper control servo motor as-
sembly.
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.
Set TemperatureVoltage
PositionResistance
Remove A/C amplifier with connectors still connected.
1. Turn ignition switch ON.
2. Change the set temperature to activate the air mix
damper control servo motor, and measure the volt
age between terminals TP and SG of A/C amplifier
connector each time when the set temperature is
changed.
HINT: As the set temperature increases, the voltage decreases.
1. Remove instrument panel.
2. Disconnect air mix damper control servo motor as
sembly connector.
Measure resistance between terminals 4 and 5 of air
mix damper control servo motor assembly connector.
While operating air mix damper control servo motor,
following the procedure on page AC±44, measure re-
sistance between terminals 5 and 3 of air mix damper
control servo motor assembly connector.
HINT: As the air mix damper control servo motor moves from
cool side to hot side, the resistance decreases.
Resistance: 4.8 ~ 7.2 k

INSPECTION PROCEDURE
± AIR CONDITIONING SYSTEMTROUBLESHOOTINGAC±43

Blinking Light M2 Air Mix Damper Control Servo Motor Circuit
CIRCUIT DESCRIPTION
The air mix damper control servo motor is controlled by the A/C amplifier and signals the air mix damper
to move to the desired position.
Diagnostic Sensor Check Detecting ConditionTrouble Area
Air mix damper position sensor value does not
change even if A/C amplifier signals the air mix
damper control servo motor to operate.
Air mix damper control servo motor

Air mix damper position sensor

Harness or connector between A/C amplifier and
A/M damper control servo motor, A/M damper
position sensor

A/C amplifier
AC±44± AIR CONDITIONING SYSTEMTROUBLESHOOTING