Low pressure switch location C5 2006?

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Axa
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Low pressure switch location C5 2006?

Post by Axa »

Hi all.
Where is the pressure switch (es?) located?
And at what PSI should it disengage?

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xantia_v6
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Re: Low pressure switch location C5 2006?

Post by xantia_v6 »

Pressure of what?

Axa
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Re: Low pressure switch location C5 2006?

Post by Axa »

Aaah sorry, posting in the Aircon forum I tought it was obvious it's the Aircon pressure switch I'm looking for.. preferably the low pressure one, if there more switches?

The clutch magnet coil got 3.9ohm. And I've removed the shim so clutch gap seemed to be good now.

I got a loos fitting on the suction pipe on the compressor. The pipe is bendt due to a previous accident so I'm waiting for a new second hand pipe.
Meanwhile I would like to jump the low pressure switch just to check it makes the compressor to engage.

I have found a contact that goes to something on the compressor on the opposite (under)side of the clutch. Is that the sensor in looking for, or is that an overhearing/temperature sensor switch?

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GiveMeABreak
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Re: Low pressure switch location C5 2006?

Post by GiveMeABreak »

The only pressure switch (Aircon Fluid Pressure Switch or Dehydrator Pressure Switch) is item 5 below:
C5 AC Pressure.PNG

Axa
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Re: Low pressure switch location C5 2006?

Post by Axa »

Thanx Mark! :-)

Any ideas on what PSI that switch engages?

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Re: Low pressure switch location C5 2006?

Post by GiveMeABreak »

Here's some info on the system that may help you.

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.

In the table below: The air conditioning compressor is cut off, if the evaporator temperature sensor is less than a low limit for 1 minute.
Exterior temperature (°C)-402103580
Low limit (°C)-1-1-100

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)-402103580
High limit (°C)44433

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)13.25141617.5192226.531
Air conditioning compressor speed (rpm)75007000600050004000300020001000
Air conditioning fluid pressure safety

The air conditioning high and low pressure safety management status is transmitted by the BSI 1 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)-40351025354580
Air conditioning compressor electrovalve (%)0303030456570100

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.


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)80453830225
So-called "ideal" high pressure ( bar)212120181616
Idle level
If the temperature of the evaporator sensor exceeds the evaporator reference value of 3°C, the BSI 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: 1.25
  • DV engine: 1.28
  • DW engine: 1.28

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Re: Low pressure switch location C5 2006?

Post by aneesh84 »

Wanted to share my experience. Yesterday the aircon specialist installed a new condensor, and filled up the gas. We started the car and were monitoring the evaporator temperature and it wont go below 16 degrees. Even after 30 minutes of car idling it never went below 14. The specialist suspected that the compressor electrovalve must be bad since it was not working at full capacity.

Today I tried starting and it was the same after start, but the moment I started driving the AC started chilling and in a few minutes the evaporator temperature went down to 3-4 Degrees. The radiator fan has been working properly throughout. I can only conclude that the AC electrovalve signal is controlled by other factors by the BSI for purposes of maintaining fuel economy. Full cooling only occurs after the car has started moving (at least the first time after starting), also I noticed on heavy acceleration, the electrovalve reduces the cooling to take less power from the engine.

In the Lexia I didnt find anywhere it actually shows the compressor electrovalve percentage signal. If anyone knows how to see that, please let me know.

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GiveMeABreak
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Re: Low pressure switch location C5 2006?

Post by GiveMeABreak »

See the section above "Dialogue with the engine ECU (CMM)"

aneesh84
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Re: Low pressure switch location C5 2006?

Post by aneesh84 »

GiveMeABreak wrote:
20 Jun 2021, 21:18
See the section above "Dialogue with the engine ECU (CMM)"
Yes but I was not able to find anywhere the current percentage of compressor electrovalve position.

I am attaching 2 screenshots. The first one is within the "Injection Menu" in Lexia, under cooling-air conditioning, where it shows the gas pressure which gives and idea of of compression being made: at idle its at 6 bars and I saw it go up to 14 bars when it was giving maximum cooling.

Image

Image

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GiveMeABreak
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Re: Low pressure switch location C5 2006?

Post by GiveMeABreak »

What's that last parameter in the first screenshot - it's covered by your windows start menu? .... open cylcle ratio?

If not there, try looking at custom parameters and see if you can add it.

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Re: Low pressure switch location C5 2006?

Post by aneesh84 »

GiveMeABreak wrote:
21 Jun 2021, 00:09
What's that last parameter in the first screenshot - it's covered by your windows start menu? .... open cylcle ratio?

If not there, try looking at custom parameters and see if you can add it.
Cooling circuit electrovalve open cycle ratio. i believe earlier models used to have two electrovalves in the thermostat housing. mine doesn't have them but still shows an error. i don't think that is relevant.

the personalised parameters showed all the same options and i couldn't find it there. anyways now my ac works well, it was only curiosity. also wanted to share that with these variable ac systems it needs to be driven around in different conditions to be tested because testing in a workshop in stationary condition, one can mistake the ac to be working suboptimally.