AC Compressor wire 2 pin.

[seanrx]

Hi all.
My C5's compressor wiring, the small 2 pin harness.
Anyone know of its function? A sensor?
It's female connector has a 10v reading.

No info in Haynes, or online. I'd like to know as I'm testing for a non working cooling fan.

[Steve Walsh]

The 2 wires to the AC Compressor operate the magnetic clutch for the compressor

[seanrx]

It does?
I have a Mk 2 car and compressor has also a yellow 3 pin plug.

Is this to clutch?

I've been watching a compressor/coil fix on YouTube. Can see a 3 and 2 pin.

[Steve Walsh]

OK

Sure mine has just a 2 pin

[white exec]

A/C compressors I've seen recently can have 1 pin (grounded –ve), 2 pin (clutch supply and Gnd), perhaps more.
Check the vehicle wiring to see where anything more than 2 pins goes.

[GiveMeABreak]

It does?
I have a Mk 2 car and compressor has also a yellow 3 pin plug.

Is this to clutch?

I've been watching a compressor/coil fix on YouTube. Can see a 3 and 2 pin.

8020 is the A/C Compressor on your vehicle. There are 2 connectors a 2 pin yellow and 2 pin black connector:

Wiring
Black connector:
8058: Compressor Valve Control
M802A: Earth

Yellow Connector:
8060: Compressor Control
M802B: Earth

Both go to the Engine Fuse Box (PSF1)

[GiveMeABreak]

Some further info on the A/C system on your vehicle as I had some time this morning - that may help with understanding the operation:

Management of the cooling compressor
Air conditioning compressor safety - Air conditioning evaporator icing safety function

To prevent icing up of the air conditioning evaporator, the BSI prohibits triggering of the air conditioning compressor in certain temperature conditions. The evaporator icing up safety function is managed by the BSI.

The air conditioning compressor is cut off, if the evaporator temperature sensor is less than a low limit for 1 minute
Exterior temperature (°C)	-40	2	10	35	80
Low limit (°C)	-1	-1	-1	0	0

The air conditioning compressor is retriggered, if the temperature returns above a high limit and the cut-off time of 1 minute has elapsed
Exterior temperature (°C)	-40	2	10	35	80
High limit (°C)	4	4	4	3	3

Cutting of the air conditioning compressor due to compressor speed
When the air conditioning compressor speed attains 8100 rpm the air conditioning compressor is cut off.
If the air conditioning compressor speed exceeds 7500 rpm for more than 10 seconds, the air conditioning compressor is cut off.

The triggering of the air conditioning compressor following a cut-off due to the speed depends on the air conditioning fluid
Air conditioning fluid pressure (Bar)	13.25	14	16	17.5	19	22	26.5	31
Air conditioning compressor speed (RPM)	7500	7000	6000	5000	4000	3000	2000	1000

Air conditioning fluid pressure safety
The air conditioning high and low pressure safety management status is transmitted by the BSI via a linear pressure sensor.
The linear pressure sensor measures the pressure of the air conditioning fluid.
The reception of pressure information is carried out by the engine ECU through a wire link.
When the pressure of the air conditioning fluid is below 2,8 bar, the air conditioning compressor is cut off. The air conditioning compressor is triggered again when the air conditioning fluid pressure increases to above 3,3 bar.
When the pressure of the air conditioning fluid is greater than 28,2 bars, the air conditioning compressor is cut off. The air conditioning compressor is triggered again when the air conditioning fluid pressure falls below 20 bars.

Safety as a function of exterior temperature
When the exterior temperature is below 3,5°C, the air conditioning compressor is cut off.
The air conditioning compressor is triggered again when the exterior temperature increases to above 4,5°C.

Safety as a function of the electrical diagnosis

• The air conditioning compressor is cut in the following conditions:
• Air conditioning compressor clutch fault
• Air conditioning compressor electrovalve fault
• Air conditioning fluid pressure sensor fault
• Blower fault (delay of 30 seconds)
• Fault in communication between the engine ECU and the built-in systems interface (BSI)
• Fault in communication between the engine fuse box and the built-in systems interface (BSI)

An evaporator sensor fault does not result in cutting off of the air conditioning compressor but rather a fixed air conditioning compressor electrovalve control value (in %) . This fixed value depends on the temperature of the air entering the evaporator (the temperature of the air entering the evaporator depends on the outside temperature, the cabin temperature and on the air intake control).

Air temperature at the evaporator intake (°C)	-40	3	5	10	25	35	45	80
Air conditioning compressor electrovalve (%)	0	30	30	30	45	65	70	100

Management of the OFF times
The safety functions implemented in the BSI 1 are associated with air conditioning compressor cut-off OFF times. The air conditioning compressor cut-off times linked to these various safety functions are not cumulative.
The cut-off time is 5 seconds for all cut-offs, only the high pressure and icing up cut-offs have a duration of 150 seconds.

Air conditioning compressor electrovalve
The externally-controlled air conditioning compressor has an electrovalve which permits regulation of the low pressure, which thus makes it possible to control the temperature of the evaporator to between 3°C and 13°C. Its purpose is to produce the quantity of cold air necessary for comfort and thus save fuel.

N.B.: When the air conditioning compressor is not clutched, the air conditioning compressor electrovalve is at 0%.

The air conditioning evaporator reference value is regulated between 3 and 13°C depending on the exterior conditions, the calculated passenger compartment temperature and the temperature reference values displayed.
In visibility mode, the air conditioning evaporator reference value is always 3°C.

Regulation of the high pressure
To prevent the air conditioning compressor from being cut off by the high pressure safety function above 24,2 bar : The air conditioning evaporator reference value increases in order to reduce the air conditioning compressor electrovalve control (in %) and therefore the capacity of the air conditioning compressor. This reference value makes it possible to maintain a high pressure which is acceptable as regards the reliability of the components of the air conditioning loop.

Air conditioning compressor electrovalve / air conditioning evaporator temperature relationship
In certain conditions (example: in a workshop at 20°C).
In order to obtain an air conditioning evaporator temperature of 3°C, the air conditioning compressor electrovalve control is approximately 50% +/- 5%.
In order to obtain an air conditioning evaporator temperature of 10°C, the air conditioning compressor electrovalve control is approximately 35% +/- 5%.

Dialogue with the engine ECU (CMM)
The engine ECU transmits reference values for control of the air conditioning compressor electrovalve and for clutching of the air conditioning compressor to the BSI 1 via the "air conditioning compressor relief reference value" information. This information may have 5 values:

• No engine ECU request
• Request for setting of the status of the air conditioning compressor clutch and of the air conditioning compressor electrovalve (valve I) (example: automatic gearbox and controlled manual gearbox gear changes)
• Request for I valve air conditioning compressor electrovalve at 50% (not used)
• Request for I valve air conditioning compressor electrovalve at 5%
• Air conditioning compressor clutching cut-off request (anti-stall)

The engine ECU informs the BSI of the status of the fan assembly (cooling fan).
The BSI provides the engine ECU with the mechanical power consumed by the air conditioning compressor.

Additional heating (PTC passenger compartment air heating resistor)
The passenger compartment air heating resistors are intended to improve the increase in the temperature of the vehicle’s passenger compartment.
The heating is assured by the cabin air heating elements located in the air conditioning unit.
The control of the passenger compartment air heating resistors (PTC) depends on the difference between the blown air reference value and the engine coolant temperature.
The blown air reference value is calculated from the exterior temperature, the temperature reference values displayed and the calculated passenger compartment temperature.
If the engine coolant temperature is lower than the blown air reference value, the passenger compartment air heating resistors (PTC) are controlled . This management permits optimisation of the vehicle’s electrical consumption.

Air recirculation management
Air recirculation at the request of the user
The air recirculation is requested via a push type button. If the air recirculation push button is pressed again, this reverses the action linked with the previous press.
On some versions, there is a recirculation control on the steering wheel with fixed centralised controls.
The management of the air recirculation is identical regardless of whether the request originates from the air conditioning panel or from the steering wheel with fixed centralised controls.

The symbol on the display is managed as follows:

• Air recirculation button activated = symbol lit
• Air recirculation button not activated = symbol off

Partial air recirculation
The partial air recirculation consists of using (via the air conditioning unit air intake flap) part passenger compartment air and part exterior air.
For all engines, a partial recirculation phase is carried out to improve the heating of the passenger compartment.
This recirculation phase takes place during the engine coolant temperature increase between 35°C and 65°C.
In the same way, total or partial air recirculation is carried out to improve the performance of the air conditioning.
The rate of air recirculation depends on the exterior temperature and the calculated passenger compartment temperature.

Automatic air recirculation with pollution sensor
A complete air recirculation phase is performed if outside air pollution is detected (NO, CO).
This function is deactivated only if there is risk of misting (hygrometry sensor).

Communication between the BSI1 and the air conditioning control panel

Automatically regulated air conditioning.
All of the reference values transmitted to the actuators of the air conditioning system are processed in the BSI and communicated to the air conditioning control panel via the COMFORT CAN.
If the communication between the BSI and the air conditioning control panel is interrupted, the air conditioning control panel switches to back-up mode.

The air conditioning control panel then behaves as if for manual air conditioning . Each reference value displayed corresponds to a fixed rate of mixing. The other actuators (distribution, blower, air intake) are in manual mode. In this case the air conditioning compressor is switched off.

Electric cooling fan unit (cooling fan)
The air conditioning requires a fan assembly to cool the air conditioning condenser.
The fan assembly control is calculated in relation to:

• Exterior temperature
• Temperature reference value displayed
• High pressure
• Vehicle speed

A high pressure referred to as "ideal" is calculated in relation to the exterior temperature and the reference values displayed.
If the high pressure measured exceeds this so-called "ideal" high pressure, the fan assembly control increases in order to reduce the high pressure measured until the "ideal" high pressure is reached.

With reference value 21°C / 21°C right
Exterior temperature (°C)	80	45	38	30	22	5
So-called "ideal" high pressure ( bar)	21	21	20	18	16	16

Idle level
If the temperature of the evaporator sensor exceeds the evaporator reference value of 3°C, the BSI1 transmits a fast idle request to the engine ECU.
There are different levels of engine speed, which can increase every 30 seconds and reduce every 5 minutes:
Level 0: 600 rpm
Level 1: 700 rpm
Level 2: 800 rpm
Level 3: 900 rpm

These speeds are speeds of rotation of the air conditioning compressor, to find out the corresponding engine speed it is necessary to divide by the air conditioning compressor drive ratio.
This air conditioning compressor drive ratio depends on the various engines:

EW engine (your vehicle): 1.25
DV engine: 1.28
DW engine: 1.28

Sun sensor
For RFTA+ versions, there is a two-directional sunlight sensor.
For the same (right/left) reference temperature displayed in AUTO mode, the sunlight sensor can produce air distribution modes and air temperatures that are different (right or left).

For example, for the same reference temperature, in right/left locked mode, the side of the vehicle receiving the most sunshine can have air to the footwells/air vents and the side receiving the least sunshine can have air to the footwells/windscreen.

[GiveMeABreak]

Some further info on the A/C system on your vehicle as I had some time this morning - that may help with understanding the operation:

Management of the cooling compressor
Air conditioning compressor safety - Air conditioning evaporator icing safety function

To prevent icing up of the air conditioning evaporator, the BSI prohibits triggering of the air conditioning compressor in certain temperature conditions. The evaporator icing up safety function is managed by the BSI.

The air conditioning compressor is cut off, if the evaporator temperature sensor is less than a low limit for 1 minute
Exterior temperature (°C)	-40	2	10	35	80
Low limit (°C)	-1	-1	-1	0	0

The air conditioning compressor is retriggered, if the temperature returns above a high limit and the cut-off time of 1 minute has elapsed
Exterior temperature (°C)	-40	2	10	35	80
High limit (°C)	4	4	4	3	3

Cutting of the air conditioning compressor due to compressor speed
When the air conditioning compressor speed attains 8100 rpm the air conditioning compressor is cut off.
If the air conditioning compressor speed exceeds 7500 rpm for more than 10 seconds, the air conditioning compressor is cut off.

The triggering of the air conditioning compressor following a cut-off due to the speed depends on the air conditioning fluid
Air conditioning fluid pressure (Bar)	13.25	14	16	17.5	19	22	26.5	31
Air conditioning compressor speed (RPM)	7500	7000	6000	5000	4000	3000	2000	1000

Air conditioning fluid pressure safety
The air conditioning high and low pressure safety management status is transmitted by the BSI via a linear pressure sensor.
The linear pressure sensor measures the pressure of the air conditioning fluid.
The reception of pressure information is carried out by the engine ECU through a wire link.
When the pressure of the air conditioning fluid is below 2,8 bar, the air conditioning compressor is cut off. The air conditioning compressor is triggered again when the air conditioning fluid pressure increases to above 3,3 bar.
When the pressure of the air conditioning fluid is greater than 28,2 bars, the air conditioning compressor is cut off. The air conditioning compressor is triggered again when the air conditioning fluid pressure falls below 20 bars.

Safety as a function of exterior temperature
When the exterior temperature is below 3,5°C, the air conditioning compressor is cut off.
The air conditioning compressor is triggered again when the exterior temperature increases to above 4,5°C.

Safety as a function of the electrical diagnosis

• The air conditioning compressor is cut in the following conditions:
• Air conditioning compressor clutch fault
• Air conditioning compressor electrovalve fault
• Air conditioning fluid pressure sensor fault
• Blower fault (delay of 30 seconds)
• Fault in communication between the engine ECU and the built-in systems interface (BSI)
• Fault in communication between the engine fuse box and the built-in systems interface (BSI)

An evaporator sensor fault does not result in cutting off of the air conditioning compressor but rather a fixed air conditioning compressor electrovalve control value (in %) . This fixed value depends on the temperature of the air entering the evaporator (the temperature of the air entering the evaporator depends on the outside temperature, the cabin temperature and on the air intake control).

Air temperature at the evaporator intake (°C)	-40	3	5	10	25	35	45	80
Air conditioning compressor electrovalve (%)	0	30	30	30	45	65	70	100

Management of the OFF times
The safety functions implemented in the BSI 1 are associated with air conditioning compressor cut-off OFF times. The air conditioning compressor cut-off times linked to these various safety functions are not cumulative.
The cut-off time is 5 seconds for all cut-offs, only the high pressure and icing up cut-offs have a duration of 150 seconds.

Air conditioning compressor electrovalve
The externally-controlled air conditioning compressor has an electrovalve which permits regulation of the low pressure, which thus makes it possible to control the temperature of the evaporator to between 3°C and 13°C. Its purpose is to produce the quantity of cold air necessary for comfort and thus save fuel.

N.B.: When the air conditioning compressor is not clutched, the air conditioning compressor electrovalve is at 0%.

The air conditioning evaporator reference value is regulated between 3 and 13°C depending on the exterior conditions, the calculated passenger compartment temperature and the temperature reference values displayed.
In visibility mode, the air conditioning evaporator reference value is always 3°C.

Regulation of the high pressure
To prevent the air conditioning compressor from being cut off by the high pressure safety function above 24,2 bar : The air conditioning evaporator reference value increases in order to reduce the air conditioning compressor electrovalve control (in %) and therefore the capacity of the air conditioning compressor. This reference value makes it possible to maintain a high pressure which is acceptable as regards the reliability of the components of the air conditioning loop.

Air conditioning compressor electrovalve / air conditioning evaporator temperature relationship
In certain conditions (example: in a workshop at 20°C).
In order to obtain an air conditioning evaporator temperature of 3°C, the air conditioning compressor electrovalve control is approximately 50% +/- 5%.
In order to obtain an air conditioning evaporator temperature of 10°C, the air conditioning compressor electrovalve control is approximately 35% +/- 5%.

Dialogue with the engine ECU (CMM)
The engine ECU transmits reference values for control of the air conditioning compressor electrovalve and for clutching of the air conditioning compressor to the BSI 1 via the "air conditioning compressor relief reference value" information. This information may have 5 values:

• No engine ECU request
• Request for setting of the status of the air conditioning compressor clutch and of the air conditioning compressor electrovalve (valve I) (example: automatic gearbox and controlled manual gearbox gear changes)
• Request for I valve air conditioning compressor electrovalve at 50% (not used)
• Request for I valve air conditioning compressor electrovalve at 5%
• Air conditioning compressor clutching cut-off request (anti-stall)

The engine ECU informs the BSI of the status of the fan assembly (cooling fan).
The BSI provides the engine ECU with the mechanical power consumed by the air conditioning compressor.

Additional heating (PTC passenger compartment air heating resistor)
The passenger compartment air heating resistors are intended to improve the increase in the temperature of the vehicle’s passenger compartment.
The heating is assured by the cabin air heating elements located in the air conditioning unit.
The control of the passenger compartment air heating resistors (PTC) depends on the difference between the blown air reference value and the engine coolant temperature.
The blown air reference value is calculated from the exterior temperature, the temperature reference values displayed and the calculated passenger compartment temperature.
If the engine coolant temperature is lower than the blown air reference value, the passenger compartment air heating resistors (PTC) are controlled . This management permits optimisation of the vehicle’s electrical consumption.

Air recirculation management
Air recirculation at the request of the user
The air recirculation is requested via a push type button. If the air recirculation push button is pressed again, this reverses the action linked with the previous press.
On some versions, there is a recirculation control on the steering wheel with fixed centralised controls.
The management of the air recirculation is identical regardless of whether the request originates from the air conditioning panel or from the steering wheel with fixed centralised controls.

The symbol on the display is managed as follows:

• Air recirculation button activated = symbol lit
• Air recirculation button not activated = symbol off

Partial air recirculation
The partial air recirculation consists of using (via the air conditioning unit air intake flap) part passenger compartment air and part exterior air.
For all engines, a partial recirculation phase is carried out to improve the heating of the passenger compartment.
This recirculation phase takes place during the engine coolant temperature increase between 35°C and 65°C.
In the same way, total or partial air recirculation is carried out to improve the performance of the air conditioning.
The rate of air recirculation depends on the exterior temperature and the calculated passenger compartment temperature.

Automatic air recirculation with pollution sensor
A complete air recirculation phase is performed if outside air pollution is detected (NO, CO).
This function is deactivated only if there is risk of misting (hygrometry sensor).

Communication between the BSI1 and the air conditioning control panel

Automatically regulated air conditioning.
All of the reference values transmitted to the actuators of the air conditioning system are processed in the BSI and communicated to the air conditioning control panel via the COMFORT CAN.
If the communication between the BSI and the air conditioning control panel is interrupted, the air conditioning control panel switches to back-up mode.

The air conditioning control panel then behaves as if for manual air conditioning . Each reference value displayed corresponds to a fixed rate of mixing. The other actuators (distribution, blower, air intake) are in manual mode. In this case the air conditioning compressor is switched off.

Electric cooling fan unit (cooling fan)
The air conditioning requires a fan assembly to cool the air conditioning condenser.
The fan assembly control is calculated in relation to:

• Exterior temperature
• Temperature reference value displayed
• High pressure
• Vehicle speed

A high pressure referred to as "ideal" is calculated in relation to the exterior temperature and the reference values displayed.
If the high pressure measured exceeds this so-called "ideal" high pressure, the fan assembly control increases in order to reduce the high pressure measured until the "ideal" high pressure is reached.

With reference value 21°C / 21°C right
Exterior temperature (°C)	80	45	38	30	22	5
So-called "ideal" high pressure ( bar)	21	21	20	18	16	16

Idle level
If the temperature of the evaporator sensor exceeds the evaporator reference value of 3°C, the BSI1 transmits a fast idle request to the engine ECU.
There are different levels of engine speed, which can increase every 30 seconds and reduce every 5 minutes:
Level 0: 600 rpm
Level 1: 700 rpm
Level 2: 800 rpm
Level 3: 900 rpm

These speeds are speeds of rotation of the air conditioning compressor, to find out the corresponding engine speed it is necessary to divide by the air conditioning compressor drive ratio.
This air conditioning compressor drive ratio depends on the various engines:

EW engine (your vehicle): 1.25
DV engine: 1.28
DW engine: 1.28

Sun sensor
For RFTA+ versions, there is a two-directional sunlight sensor.
For the same (right/left) reference temperature displayed in AUTO mode, the sunlight sensor can produce air distribution modes and air temperatures that are different (right or left).

For example, for the same reference temperature, in right/left locked mode, the side of the vehicle receiving the most sunshine can have air to the footwells/air vents and the side receiving the least sunshine can have air to the footwells/windscreen.

[ozvtr]

There will be two connectors on the compressor. One yellow and one black. The yellow one is for the clutch, the black is for the electrovalve. The electrovalve is on the "back end" of the compressor.

Air conditioning compressor electrovalve
The externally-controlled air conditioning compressor has an electrovalve which permits regulation of the low pressure, which thus makes it possible to control the temperature of the evaporator to between 3°C and 13°C. Its purpose is to produce the quantity of cold air necessary for comfort and thus save fuel.

N.B.: When the air conditioning compressor is not clutched, the air conditioning compressor electrovalve is at 0%.

The air conditioning evaporator reference value is regulated between 3 and 13°C depending on the exterior conditions, the calculated passenger compartment temperature and the temperature reference values displayed.
In visibility mode, the air conditioning evaporator reference value is always 3°C.

Effectively the electrovalve controls how much Compressing the compressor does. It's more efficient than switching the clutch in and out to regulate the refrigerant.

If the cooling fan(s) stop working it's usually the electronic speed controller or the speed control resistor (in the fan unit). Depends on which system you have. If there is a failure of the engine ECU (the engine ECU controls the fans) or wiring, the fail-safe is that the fans run continuously. However the power for the fan(s) comes from the BSM!

[GiveMeABreak]

The above info is specifically for the system on the OP's C5 with RFTA (regulated A/C) and the wiring diagram extract I put up 2 posts ago show the 2 connectors. This should cover the system's operation in enough detail.

[ozvtr]

I'm testing for a non working cooling fan.

[ozvtr]

8020 is the A/C Compressor on your vehicle. There are 2 connectors a 2 pin yellow and 2 pin black connector:

Sorry, missed that. Was concentrating on OPs fan controller problem.

[seanrx]

Marc.
Many thanks for your post. This confirms that I have an electrical fault.

A new t'stat is fitted, but no change in fan function.
I've been testing for continuity and that 2 pin plug is my final check once I find an old harness and wiring.

Also, my neighbor used his hi tec code reader on my car and found many 'intermittent' sensor/coherence/earth faults:

Ac, fan, thermistor, inlet manifold, cruise control. Its quite a list!

So I will do the basics first, strip and clean body ground points and multimeter check fuses, not just a visual check of them.
Am sure it won't fix everything, but I need a 'base' to work off.

[GiveMeABreak]

Ok, best of luck tracking them down.