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Air conditioning diagnosis and repair

Publitest diagnosis and repair of air-conditioning

A/C control: manual / automatic

workings & design

auto A/C Control Unit


1 display -> on the driver side.
2 air recirculation.
3 air distribution : front air vent.
4 air distribution : air vent to the footwell.
5 air distribution : 'high' air vent.
6 display -> on the passenger side.
7 misting / defrost.
8 rearscreen defrost.
9 temperature selection -> on the driver side.
10 ventilation (blower) speed selection -> right side.
11 ventilation (blower) speed selection -> left side.
12 cabin temperature sensor.
13 auto mode AUTO.
14 A / C activation compressor deactivation ECON.
15 temperature selection -> on the passenger side.
16 air recirculation through air quality monitoring.

workings & design



diagram caption

G65 A/C refrigerant high pressure HP sensor.
G89 intake air temperature (IAT) sensor *.
G107 sunlight sensor.
G150 cabin temperature sensor / lateral air vent / / on the driver side.
G151 cabin temperature sensor / lateral air vent / / on the passenger side.
G238 air quality sensor - AQS.
G261 cabin temperature sensor / -> floor / / on the driver side.
G262 cabin temperature sensor / -> floor / / on the passenger side.
G263 temperature sensor of the evaporator.
Gxxx feedback potentiometer / air distribution flap servomotor.
J126 cabin blower control module.
J255 A/C control unit.
K16 diagnosis connector (DLC).
N280 external control solenoid.
V2 cabin blower.
V70 air distribution flap servomotor / centre flap.
V71 dynamic flap servomotor.
V107 defrost flap servomotor.
V113 air recirculation motor.
V158 air mix motor / / on the passenger side.
V159 air mix motor / / on the driver side.
Not shown :
G56 cabin temperature sensor / A/C Control Unit.
* according to model year.

replacement

After the substitution of the A/C C. U. , the adaptive parameters need refreshing / encoding.
Select in the following order.
Use a diagnosis equipment :

Publitest diagnosis and repair of air-conditioning

A/C control: manual / automatic

location of the components

under the bonnet



in the cabin




 B24 Cabin fuses box
 B25 Motor compartment fuses box
 C1 Low pressure drain/refill connection
 C11 Motoventilator of the A/C condenser
 C12 Outside temperature sensor
 C13 Condenser
 C15 Evaporator
 C2 (HP) high pressure drain/refill connection
 C20 A/C control unit
 C27 Impulses shock absorber
 C3 A/C compressor
 C34 Dehydrator/drier
 C6 Pressure reducer - gauged opening
 C7 Pressure switch
 H5 Motoventilator of the engine coolant circuit
 P24 Cabin relay panel
 P25 Motor compartment relays panel

pressures/temperature

general instruction

With the motor running.
A-C running.
Cabin filter in perfect shape (if fitted).
A-C controls position.
Air distribution : central air vents at maxi opening.
Cabin air distribution : recirculation.
Air temperature in the cabin : maximum cold.
Blower speed : maxi.

particular instruction

Motor bonnet closed.
Hot engine (after one engagement of the motor-driven fan).
A-C running for at least 10 minutes.
Doors closed, windows avant open.

checking

Connect the inspection equipment to the high and low pressure couplings.
Keep the engine speed at 2000 rpm.
Control the pressures.
The readings should be in line with the reference values.

outside temperature (°C)input pressure of the compressor (LP) bar
15,004,70+ -
20,005,60+ -
25,006,60+ -
30,007,60+ -

Condenser

Replacement labor time:2.90 h

surroundings removal





Remove :
  • The front bumper.
  • The A/C hose flange ->.
Draw a line 1 to mark the position of the latch holder on the top of the wings 2.
Remove :
  • The screws Vs fastening the latch-carrier stiffener x4.
  • The shock absorber screws Vs2.
Make to slide :
  • The latch holder Ps.
Install :
  • The fastening Vs Ot screws M10x120.
  • The latch-carrier spacers Ot Ref 10-222 A17.

component removal



Remove on the latch-carrier bracket:
  • The screws Vs fastening the bracket Su / left side / right side.
Split :
  • The unit coolant radiator / condenser Rd rearwards.
Remove :
  • The couplings 1 of the cooling gas ducts of the condenser.
  • The screws 2 fastening the condenser.
Free the condenser from the radiator.

A/C control unit

component removal



Remove :
  • The radio set 2.
Extract :
  • The lower trim 1a.
  • The upper shield 1b.
Unclip :
  • The fastenings At.
Extract :
  • The A/C control unit C20 frontwards.
  • The electrical connections.

nota:

After the substitution of the A/C C. U. , the adaptive parameters need refreshing / encoding.

A/C compressor

Replacement labor time:1.00 h

accessibility

  • Disconnect the battery.
Remove :
  • The lower shield sheet of the motor.

surroundings removal

Remove :
  • The engine sound-proofing material.

component removal


Remove :
  • The connector.
  • The couplings 1 of the cooling gas ducts of the compressor.
  • The screws of the compressor 2.
  • The spacers 3.
  • The A/C compressor.

Dehydrator/drier

structure and managment

The drier-filter is also known as filter-tank.
When the liquefied gas returns to its gas form, it crosses the drier-filter which serves at once as cooling liquid tank, moisture extractor and filter.
There is often a sight feed glass to check the quality of the liquefied gas.

vehicle test conditions

Best possible, vehicle on a hoist.

general instruction

Disconnect the battery.
Empty the gas cooling circuit through the reload equipment.
Put caps on the ducts right after disconnection, to avoid any dust and moisture pollution.

accessibility

Remove :

component removal


According to the versions :
Unscrew couplings of the cooling gas ducts on the filter-tank B2.
Remove :
  • The 2 screws fastening the filter-tank bracket on the condenser.
  • The drier-filter-tank C4 upwards.

component removal


According to the versions :
  • A drier cartridge is integrated to the condenser.
Remove :
With adequate tool, remove the drier housing cap A3.
Extract the drier cartridge C34 while gaining support from the opening.
Reassembly :
Proceed reversing the order of the removal without forgetting to renew the O'-ring seal.

Publitest diagnosis and repair of air-conditioning

A/C control: manual / automatic

105 cv 1.9 Tdi motor: BLS

under the bonnet



in the cabin










caption

1 A/C refrigerant high pressure HP sensor G65.
2 intake air temperature (IAT) sensor G89.
3 external control solenoid N280.
4 outside temperature sensor.
5a low pressure drain/refill connection.
5b (HP) high pressure drain/refill connection.
6 air quality sensor - AQS G238.
7 air duct.
8 cabin temperature sensor on the driver side G150.
9 dashboard instrument subsystem.
10 air grid.
11 sunlight sensor G107.
12 cabin temperature sensor ambient temperature G56.
13 A/C control unit J255.
14 cabin temperature sensor on the passenger side G151.
15 air duct.
16 cabin filter.
17 diagnosis connector (DLC).
18 water drain valve.
19 air mix motor -> floor on the passenger side V159.
20 temperature sensor of the evaporator G263.
21 water drain hole.
22 cabin temperature sensor -> floor on the driver side G261.
23 air distribution flap servomotor central V70.
24 auxiliary heater.
25 air mix motor on the driver side V158.
26 air distribution flap servomotor dynamic V71.
27 air recirculation motor V113.
28 cabin temperature sensor -> floor on the passenger side G262.
29 cabin blower control module J126.
30 defrost flap servomotor V107.
Earth :
44 earth.
379 earth.
673 earth.

fuse(s)

cabin fuses box

location



F4 fuse of the pressure switch / air quality sensor - AQS.
F4 fuse of the A/C control unit 2007 ->.
F16 fuse of the A/C control unit.
F22 fuse of the cabin blower control unit.
F37 fuse of the A/C control unit.
F46 fuse of the A/C control unit -> 2006.

motor compartment fuses box

location




Cartridge fuses box :
MF3 cartridge fuse of the engine coolant motor-driven fan.
Fuse and relay box / motor :
According to the versions.
F8 fuse of the control unit of the engine coolant motor-driven fan -> 2006.
F38 fuse of the control unit of the engine coolant motor-driven fan 2006.
F24 fuse of the control unit of the engine coolant motor-driven fan 2007 ->.
F54 cartridge fuse of the engine coolant motor-driven fan -> motor F.S.I.

pressures/temperature

general instruction

With the motor running.
A-C running.
Cabin filter in perfect shape (if fitted).
A-C controls position.
Air distribution : central air vents at maxi opening.
Cabin air distribution : recirculation.
Air temperature in the cabin : maximum cold.
Blower speed : maxi.

particular instruction

Motor bonnet closed.
Hot engine (after one engagement of the motor-driven fan).
A-C running for at least 10 minutes.
Doors closed, windows avant open.

checking

Connect the inspection equipment to the high and low pressure couplings.
Keep the engine speed at 2000 rpm.
Control the pressures.
The readings should be in line with the reference values.

outside temperature (°C)input pressure of the compressor (LP) bar
15,004,70+ -
20,005,60+ -
25,006,60+ -
30,007,60+ -

Connector

A/C Control Unit

A/C control unit


T12 12 pins connector :
1 air mix motor +/- / left side.
2 air mix motor +/- / left side.
3 defrost flap servomotor +/-.
4 defrost flap servomotor +/-.
5 air distribution flap servomotor centre air vent +/-.
6 air distribution flap servomotor centre air vent +/-.
7 air recirculation motor +/-.
8 air recirculation motor +/-.
9 dynamic flap servomotor +/-.
10 dynamic flap servomotor +/-.
11 air mix motor +/- / right side.
12 air mix motor +/- / right side.

A/C control unit


T16d 16 pins connector :
1 feed system sunlight sensor.
2 electronic earth.
3 A/C refrigerant high pressure HP sensor.
4 external control solenoid.
5 heated seats / left side.
6 heated seats / right side.
7 fuse of the A/C control unit, + permanent option.
12 fuse of the A/C control unit, + permanent.
13 fuse of the A/C control unit, + permanent.
14 fuse of the A/C control unit, + permanent.
16 earth.

A/C control unit


T16e 16 pins connector :
5 cabin temperature sensor / / left side.
6 cabin temperature sensor / / right side.
7 air quality sensor - AQS.
9 sensor / heated seats / / right side.
10 sensor / heated seats / / left side.
12 CAN L.
13 CAN H.
14 sunlight sensor signal / / right side.
15 sunlight sensor signal / / left side.

A/C control unit


T20 20 pins connector :
1 outside temperature sensor.
2 feedback potentiometer / air mix motor / / left side.
3 feedback potentiometer / air mix motor / / right side.
4 feedback potentiometer defrost flap servomotor.
5 feedback potentiometer / air distribution flap servomotor / -> centre air vent.
6 feedback potentiometer / air recirculation motor.
7 feedback potentiometer / dynamic flap servomotor.
8 cabin temperature sensor / -> floor / / right side.
9 cabin temperature sensor / -> floor / / left side.
10 intake air temperature (IAT) sensor.
11 temperature sensor of the evaporator.
14 electronic earth.
19 control instruction of the fan unit.
20 feedback signal of the fan speed.

Engine control unit - ECU

connector


T94 94 pins connector.

connector


T60 60 pins connector.

Checking


temperature sensor of the evaporator

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 : 5 volts.
Component resistance KOhm :
  • Resistor : 9 +/- 2% at 0 °C.
  • Resistor : 6,9 +/- 2% at 5 °C.
  • Resistor : 5,4 +/- 2% at 10 °C.
  • Resistor : 4,3 +/- 2% at 15 °C.
  • Resistor : 3,4 +/- 2% at 20 °C.


cabin temperature sensor

2 pins connector



identification

G89 intake air temperature (IAT) sensor.

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 : 5 volts.
Component resistance KOhm :
  • Resistor : 3,28 +/- 2% at 0 °C.
  • Resistor : 2,54 +/- 2% at 5 °C.
  • Resistor : 2,0 +/- 2% at 10 °C.
  • Resistor : 1,57 +/- 2% at 15 °C.
  • Resistor : 1,25 +/- 2% at 20 °C.
  • Resistor : 1,0 +/- 2% at 25 °C.
  • Resistor : 0,8 +/- 2% at 30 °C.


external control solenoid valve of the A/C compressor

2 pins connector



workings & design

The solenoid control valve N280 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 : 12 +/- 2 KOhm.
  • Supply voltage : 12 volts pin 1.


cabin temperature sensor

2 pins connector



identification

G151 air temperature in the cabin / right side.
G152 air temperature in the cabin / left side.
G261 air temperature in the cabin / -> floor / left side.
G262 air temperature in the cabin / -> floor / right side.

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 : 5 volts.
Component resistance KOhm :
  • Resistor : 23 +/- 2% at 5 °C.
  • Resistor : 18,5 +/- 2% at 10 °C.
  • Resistor : 15 +/- 2% at 15 °C.
  • Resistor : 12,2 +/- 2% at 20 °C.
  • Resistor : 10 +/- 2% at 25 °C.
  • Resistor : 8,5 +/- 2% at 30 °C.
  • Resistor : 6,8 +/- 2% at 35 °C.


air distribution flap servomotor

6 pins connector



identification

V70 air distribution flap servomotor / central.
V71 dynamic flap servomotor.
V107 defrost flap servomotor.
V113 air recirculation motor.
V158 air mix motor / / on the driver side.
V159 air mix motor / / on the passenger side.

The system uses 1 motors under direct current voltage.
Two power supply wires help create a polarity inversion to drive the motors.
The motor(s) is (are) linked to a feedback potentiometer.
The feedback signal transferred to the C. U. belongs to the linear type.

caption

1 supply voltage : 5 volts.
2 feedback potentiometer signal.
3 earth.
4 / 5 power supply voltage +/- motor.
6 power supply voltage +/- motor.

accessibility

Contact us.

checking process

Use a diagnosis equipment :
  • Actuators checking.
  • Parameters checking.
Please refer to the paragraph below :
  • -> circuit diagram.
Features :
  • Resistor : 70 +/- 30 Ohm.
  • Channels : 4 / 5 6.
  • Supply voltage : 12 volts.
Feedback potentiometer :
  • Resistor : 4,8 +/- 0,8 KOhm.
  • Channels : 1 3.
  • Supply voltage : 5 volts.
It is possible to read the resistance value of the feedback potentiometers only directly on the servomotor (parallel circuit).
Check the electrical circuit :
Continuity check between the connector of the servomotor and the A/C C. U. socket.
Insulation test - to earth - for the socket pins.
Insulation test - to + - for the socket pins.


A/C refrigerant high pressure HP sensor

3 pins connector



identification

G65 A/C refrigerant high pressure HP sensor.

workings & design

A piezo-electric sensor keeps permanently the A/C system informed of the circuit pressure before the compressor.
The sensor's signal appears as duty cycle RCO .
The A/C C. U. activates the compressor clutch, when the duty cycle is higher than 12 % and lower than 87 %, if no compressor shut-off condition is reached.
Nota :
  • Should the sensor connector be disconnected, the compressor will not start.

caption

1 earth supply voltage : 0 volts.
2 signal of the sensor % PWM.
3 supply voltage : 5 volts.

sensor checking

Use a diagnosis equipment :
  • Parameters checking.
Voltage :
  • Supply voltage : 5 volts.
Prerequisites :
  • Switched on.
  • Engine off.
Signal of the sensor PWM 20 -> 25 %.
  • Correct sensor.
Signal of the sensor PWM > 90 %.
  • A/C refrigerant high pressure HP sensor = faulty.
Signal of the sensor PWM < 5 %.
  • A/C refrigerant high pressure HP sensor = faulty.
  • Coolant circuit = empty.
Outside temperature between 20°C and 30°C :
  • Cold motor (ambient temperature).
Read value PWM :
  • Signal of the sensor 12 % -> pressure 1,8 bar.
  • Signal of the sensor 50 % -> pressure 16 bar.
  • Signal of the sensor 87 % -> pressure 32 bar.
Test the power supply :
Insulation test - to + - for the socket pins 1 - 2.
Insulation test - to earth - for the socket pins 3 - 2.
Continuity check between the connector and the A/C C. U. socket.


cabin blower control module

6 pins connector



workings & design

When the cabin blower is duly activated, and if the A/C C.U. does not detect any trouble, the rotation speed of the cabin blower (fresh air) is transmitted at any time to the air vent unit J126 as a rectangular signal.
This rectangular signal is built as a 50 % constant duty cycle; the frequency variation represents the rotational speed regulation of the cabin blower (fresh air).
  • Example: for a 3000 rpm rotational speed of the cabin blower, the rectangular signal frequency is 150 Hz.
When the air vent C. U. J126 detects a trouble, it sends a 10 Hz (frequency) rectangular signal to the A/C C. U. which aknowledges the trouble presence.

checking process

Use a diagnosis equipment :
  • Actuators checking.
  • Parameters checking.
Channel allocation :
1 pulsated modulated signal.
2 feedback signal from the cabin blower.
3 earth.
4 feed system 12 V.
Check the electrical circuit :
Insulation test - to earth - for the socket pins 1 / 2 / 4.
Insulation test - to + - for the socket pins 1 / 2 / 3.
Continuity check between the connector J126 and the A/C C. U. socket.
Earth checking.
Test the power supply.


sunlight sensor

4 pins connector



workings & design

Starting from 2000 :
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.

caption

1 sunlight sensor signal -> left side.
2 supply voltage : 5 volts.
3 electronic earth.
4 sunlight sensor signal -> right side.

checking process

Use a diagnosis equipment :
  • Parameters checking.
Component test :
Between the pins 1 / 4 and the earth -.
  • -> check the signal variation on the channels 1 4 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.
Test the power supply.


air quality sensor - AQS

3 pins connector



workings & design

G238 air quality sensor - AQS.
The air quality sensor G238 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. J255.

caption

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 through air quality monitoring.
  • Reach the quality sensor, keeping it connected.
  • Wait for 2 minutes.
  • Spray smoke or gas CO2 towards the sensor G238.
  • Observe the servomotor action while in automatic recirculation mode.
Signal check :
Check the signal variation on the channels 3 2 with a voltmeter.
  • Pulsated modulated signal %.
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.

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