Control of the components of the air conditioning

Connector

A/C Control Unit

A/C control unit

1 16 pins connector.

fuse and relay box

A/C control unit

3 14 pins connector.

A/C control unit

2 4 pins connector.

Engine control unit – ECU

connector

M 96 pins connector.

connector

F 58 pins connector.

Checking

Cabin temperature sensor

2 pins connector

identification

Cabin temperature sensor air vent.

workings & design

This is a NTC sensor (negative temperature coefficient); as the temperature increases, the more its resistance decreases.

According to the versions :
  • Two sensors monitor the temperature on the right and left sides of the cabin.
  • Two sensors monitor the temperature on the lower and central exits in the cabin .

checking process

Use a diagnosis equipment :
  • Parameters checking.
Voltage :
  • Supply voltage : 0 5 volts.
Component resistance KOhm :
  • Resistor : 20 +/- 10% at 10 °C.
  • Resistor : 12,5 +/- 10% at 20 °C.
  • Resistor : 9,5 +/- 10% at 25 °C.
  • Resistor : 8 +/- 10% at 30 °C.
  • Resistor : 6,5 +/- 10% at 35 °C.

Temperature sensor of the evaporator

3 pins connector

workings & design

The sensor data is used by the C. U. to manage the cold outpout.

The monitoring of the evaporator temperature allows the A/C C.U. to regulate the cold production in accordance to the customer temperature request and to the mist build-up risk.

In order to avoid frosting the evaporator, the compressor supply is cut off when the temperature nears 0° C.

sensor checking

Use a diagnosis equipment :
  • Parameters checking.
Features :
  • Resistor : 9,0 +/- 10% KOhm at 0 °C.
  • Resistor : 5,5 +/- 10% KOhm at 10 °C.
  • Resistor : 3,4 +/- 10% KOhm at 20 °C.
Signal check :
  • Linear voltage signal : 0 5 volts.

Air distribution flap servomotor

4 pins connector

workings & design

The group of the air distribution motors is managed by a unique multiplex link, “LIN BUS” typ.

At idle 1, a multiplexed frame under a 12 +/- 1 V tension runs along the whole common bus. By sending an instruction on the bus, it is possible to detect an alteration of the digital signal 2.

checking process

Use a diagnosis equipment :
  • Actuators checking.
  • Parameters checking.
Channel allocation :

Pin 1 earth.

Pin 2 multiplexed signal IN.

Pin 3 multiplexed signal OUT.

Pin 4 feed system 12 V.

Check the electrical circuit :

Insulation test – to earth – for the socket pins 2 / 4 / 3.

Insulation test – to + – for the socket pins 1 / 2 / 3.

Continuity check between the connector and the A/C C. U. socket.

Earth checking.

Test the power supply.

Air quality sensor – AQS

3 pins connector

workings & design

The air quality sensor T306 is an electronic device which acts on the recirculation flap, should the pollution index exceed the pre-defined harm thresholds. Consequently, polluted air does not enter the cabin. When conditions are back to normal, the air quality control brings the flap back in its previous position. It is set under the windscreen, along the dynamic air access.

The sensitive element is warmed-up and regulated to a constant 350°C temperature.

The sensor sends a % PWM signal within 40 seconds after power connection.

The signal PWM is handled directly by the A/C C.U..

1 power supply.

2 earth.

3 pulsated modulated signal %.

checking process

Use a diagnosis equipment :
  • Parameters checking.
Component test :
  • Start the engine.
  • Press auto mode.
  • Press air recirculation.
  • Reach the quality sensor, keeping it connected.
  • Wait for 1 minutes.
  • Spray smoke or gas CO2/NO2 towards the sensor.
  • Observe the servomotor action while in automatic recirculation mode.
Signal check :

Connect the ohmmeter between the pins 2 3.

Check the signal variation on the channels 2 3 with a voltmeter.

Reference signal PWM :

Polluted gases detection NO2.

  • Signal 55 -> 95 %.

Polluted gases detection CO2.

  • Signal 5 -> 45 %.

Permanent troubles.

  • Signal 95 % >.
Check the electrical circuit :

Continuity check between the connector and the A/C C. U. socket.

Insulation test – to earth – for the socket pins.

Insulation test – to + – for the socket pins.

Earth checking.

Test the power supply 13.5 V.

External control solenoid valve of the A/C compressor

2 pins connector

workings & design

The solenoid control valve N9/7 y1 is electically piloted by the A/C C. U..

It receives a control signal which allows to force a differential pressure level in line with a swash plate position, that is to say with a clearly defined cold output of the compressor.

The control is achieved through a pulsated modulated current 500 Hz . The cubic capacity will result from the duty cycle of this signal.

The solenoid valve signal changes according to the evaporator exit temperature and to the pressure in the HP circuit.

  • 100 % = maximal cubic capacity.
  • Coolant gas pressure > 35 bar.
  • 20 % = minimal cubic capacity.
  • Coolant gas pressure 5 bar.

By OFF or ECON modes, the valve which controls the compressor is not activated (no duty signal).

By AUTO mode, with LOW temperature selected, the valve which controls the compressor is activated (display of a rectangular duty signal, cycle width between 75% and 100%).

checking process

Use a diagnosis equipment :
  • Parameters checking.
Features :
  • Channels : 1 2.
  • Resistor : 11 +/- 1,5 KOhm.
  • Supply voltage : 12 volts pin 1 2.

Outside temperature sensor

2 pins connector

workings & design

This is a NTC sensor (negative temperature coefficient); as the temperature increases, the more its resistance decreases.

checking process

Use a diagnosis equipment :
  • Parameters checking.
Voltage :
  • Supply voltage : 4,5 +/- 0,5 volts.
Features :
  • Resistor : 9,2 +/- 0,8 KOhm at 0 °C.
  • Resistor : 5,2 +/- 0,5 KOhm at 10 °C.
  • Resistor : 3,0 +/- 0,5 KOhm at 20 °C.
  • Resistor : 2,0 +/- 0,20 KOhm at 30 °C.

Cabin temperature sensor

4 pins connector

workings & design

The cabin temperature sensor B10/4 / in the cabin under the dashboard.

This is a NTC sensor (negative temperature coefficient); as the temperature increases, the more its resistance decreases.

The sensor is made of :
  • A temperature sensor.
  • A micromotor powering a turbine in order to blow air on the sensors.

1 pin feed system micromotor .

2 pin feed system micromotor +.

3 pin cabin temperature sensor.

4 pin cabin temperature sensor.

sensor checking

Use a diagnosis equipment :
  • Condition check.
Features :
Cabin temperature sensor :
  • Channels : 3 4.
  • Resistor : 4,3 +/- 10% kOhm at 10 °C.
  • Resistor : 2,7 +/- 10% kOhm at 20 °C.
  • Resistor : 2,3 +/- 10% kOhm at 25 °C.
Micromotor :
  • Supply voltage : 12 volts.
  • Channels : 1 2.

Sunlight sensor

4 pins connector

workings & design

It is made of two sensors. Each one is able to read the sunlight in the cabin, on the right and left sides.

According to the sunlight level, the recorded data weigh on :
  • The cabin blower speed.
  • The distribution flaps position.

2 sunlight sensor signal -> right side.

3 sunlight sensor signal -> left side.

4 electronic earth.

checking process

Use a diagnosis equipment :
  • Parameters checking.
Component test :

Between the pins 2 / 3 and the earth .

  • -> check the signal variation on the channels 2 3 with a voltmeter.

The signal voltage changes according to the occultation or the lighting of the sunlight sensor.

  • Sunlight level / maximum 3,0 > / volts.
  • Occultation < 1,0 volts.
Check the electrical circuit :

Continuity check between the connector and the A/C C. U. socket.

Insulation test – to earth – for the socket pins.

Insulation test – to + – for the socket pins.

Earth checking.

Cabin blower control module

2 pins connector

4 pins connector

workings & design

From 06/2010.

A32m1 cabin blower control module.

The cabin blower motor is actuated through a linear control module. The control voltage of the cabin blower is created by a PWM signal. The average voltage of the control signal varies from 3,0 volt, as the setting of the minimum speed to more or less 12,8 volts for the maximum speed. The blower is cut-off when its control voltage is below 0,5 volt.

checking process

Use a diagnosis equipment :
  • Actuators checking.
  • Parameters checking.
  • Lay an oscilloscope.

Channel allocation / 4 pins connector:

1 earth.

2 free.

3 power supply voltage of the cabin blower +12v.

4 control signal of the cabin blower module PWM %.

2 pins connector :

1 power supply of the motoventilator +.

2 power supply of the motoventilator .

Check the electrical circuit :

Insulation test – to earth – for the socket pins 2/3/4.

Insulation test – to + – for the socket pins 1/2/4.

Continuity check between the connector X1 and the A/C C. U. socket.

Earth checking.

Test the power supply.

Signal check :

Lay an oscilloscope.

Tension adjustment 2V / units.

Initial adjustment / frequency 0,5 s.

The trace of the multiplexed signal resulting from an instruction or from a distribution / mixing order can be read on an oscilloscope on the channel 4 and the earth 1.

Cabin blower control module

4 pins connector

workings & design

Until 05/2010.

A32/m1 cabin blower control module.

The modul receives from the A/C unit a variable voltage, which varies according to the requested motorfan speed.

This rectangular signal is built as a % variable duty cycle; the cycle variation represents the rotational speed regulation of the cabin blower (fresh air).

cabin blower control module

1 earth.

2 pulsated modulated signal cabin blower control %.

3 cabin blower control .

4 feed system cabin blower control module +12v.

checking process

Use a diagnosis equipment :
  • Actuators checking.
  • Parameters checking.
Signal check :
  • Pulsated modulated signal %.
  • Pin 2.
Parameters checking :

Speed 1 reference voltage 3,0 V +/- 1,0.

Speed 4 reference voltage 5,5 V +/- 1,0.

Speed 8 reference voltage 12,5 V +/- 1,5.

Cabin temperature sensor

2 pins connector

identification

Cabin temperature sensor air vent.

workings & design

This is a NTC sensor (negative temperature coefficient); as the temperature increases, the more its resistance decreases.

According to the versions :
  • Two sensors monitor the temperature on the right and left sides of the cabin.
  • Two sensors monitor the temperature on the lower and central exits in the cabin .

checking process

Use a diagnosis equipment :
  • Parameters checking.
Voltage :
  • Supply voltage : 0 5 volts.
Component resistance KOhm :
  • Resistor : 20 +/- 10% at 10 °C.
  • Resistor : 12,5 +/- 10% at 20 °C.
  • Resistor : 9,5 +/- 10% at 25 °C.
  • Resistor : 8 +/- 10% at 30 °C.
  • Resistor : 6,5 +/- 10% at 35 °C.

© Fluxea 2019