sensor TOYOTA SUPRA 1995 Service Owner's Manual

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

Air Inlet Damper Control Servo Motor Circuit
CIRCUIT DESCRIPTION
The air inlet damper control servo motor is controlled by the A/C amplifier and signals the air inlet damper
to move to the desired position.
ConditionTrouble Area

Air inlet damper position sensor

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

A/C amplifierAir mix damper position sensor value does not
change even if A/C amplifier signals the air mix
damper control servo motor to operate.
AC±46± AIR CONDITIONING SYSTEMTROUBLESHOOTING

Blinking Light LO HI Air Outlet 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 outlet
damper control servo motor assembly.
Trouble AreaDiagnostic Sensor Check Detecting ConditionLight
LO
HI
Short to ground or power source circuit in air
outlet damper position sensor circuit.
Air outlet damper position sensor value does
not change even if A/C amplifier signals the air
outlet damper control servo motor to move.

Air outlet damper position sensor

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

A/C amplifier
AC±48± AIR CONDITIONING SYSTEMTROUBLESHOOTING

(See page IN±30).
AC±50,
Check voltage between terminals TPM and SG of A/C amplifier connector.
Check and replace A/C amplifier.
Repair or replace harness or connector.
Check harness and connector between A/C amplifier and max. cool
damper control servo motor assembly (See page IN±30).
Replace max. cool damper control servo motor
assembly.
Check air outlet damper position 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.
ResistanceDamper Position
Resistance: 4.7 ~ 7.2 k

While operating air outlet damper control servo motor,
as in the procedure on page AC±50, measure resist-
ance between terminals TPM and SG of air outlet servo
motor assembly connector.
Resistance
HINT: As the air outlet servo motor moves from FACE side
to DEF side, the resistance decreases gradually without
interruption.
Measure resistance between terminals 4 and 5 of air
outlet damper control servo motor assembly connector.
1. Remove instrument panel.
2. Disconnect air outlet damper control servo motor as±
sembly connector.
HINT: As the air outlet damper control servo motor is moved from
VENT side to DEF side, the voltage decreases gradually
without interruption.
Mode SwitchVoltage
1. Remove A/C amplifier with connectors still con±
nected.
2. Turn ignition switch ON
FACE
FACE
DEF
DEF
INSPECTION PROCEDURE
± AIR CONDITIONING SYSTEMTROUBLESHOOTINGAC±49

Blinking Light HI Air Outlet Damper Control Servo Motor Circuit
CIRCUIT DESCRIPTION
This circuit turns the servo motor and changes each mode damper position by the signals from the A/C
amplifier. When the AUTO switch is on, the A/C amplifier changes the mode automatically between
(FACE), (BI±LEVEL) and (FOOT) according to the temperature setting.
Trouble AreaDiagnostic Sensor Check Detecting Condition

Air outlet damper control servo motor

Air outlet damper position sensor

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

A/C amplifier Air outlet damper position sensor value does not
change even if A/C amplifier signals the air outlet
damper control servo motor.
AC±50± AIR CONDITIONING SYSTEMTROUBLESHOOTING

Back Up Power Source Circuit
CIRCUIT DESCRIPTION
This is the back up power source for the A/C amplifier. Power is supplied even when the ignition switch is off
and is used for diagnostic sensor check memory, etc.
AC±52± AIR CONDITIONING SYSTEMTROUBLESHOOTING

A C Control Assembly Circuit
CIRCUIT DESCRIPTION
This circuit includes the control switch circuit and the LED circuit in the A/C control Assembly.
The A/C amplifier always searches which switch is operated and drives the LED according to A/C control opera-
tion or diagnostic sensor check operation.
AC±66± AIR CONDITIONING SYSTEMTROUBLESHOOTING