Help Required Air-Con (C5-X7)

[GiveMeABreak]

Ok so here goes:

Pressing the AUTO switch on the Driver / Passenger temperature control knob so that the are illuminated puts the system on automatic mode. The symbol will have an 'A' within the circle on the display LED.

This is the preferred mode as it allows the system to have fully automatic and simultaneous control of these functions:

• The Air Flow
• The Temperature in the passenger compartment (including dual zones for driver and passenger on systems with the dual zone unit).
• The Air Distribution
• The Air Conditioning
• Automatic Air Recirculation

This should be the default setting as it uses the internal air quality sensors to determine whether there are any pollutants entering the vehicle so it can close of external air automatically for a period of time.

Although the Air quality sensors can detect most hydrocarbons such as Benzene, Toluene, and gasses such as Nitrogen Dioxide, NO2 (NOx emitted by Diesels), Ozone and Sulphur Dioxide, they can't account for our 4 legged friends or the local farmer muck-spreading. So you'll have to put up with bad smells unfortunately.

So if you were passing through the rural Welsh country side and came across Dai the tractor, you might want to press the Air Re-circulation button once:

This will close off the external air from entering the system. As soon as possible, press it one more time to return to Auto mode. It really is not recommended to have Air-recirculation on for long as you are basically re-breathing exhaled air and carbon dioxide.

The Auto mode will allow the sensors to detect harmful / unpleasant gasses & hydrocarbons and automatically close off the external air for a short period, as well as keeping the air flow distribution and temperature / humidity levels at the optimum levels.

[Estately]

Marc,
Thank you for your detailed reply. After 3 C5's there are still things to learn. The cars' manuals in my opinion simply do not explain or clarify the settings available which given the technology available is a disappointment.
What I forgot to say in my previous diatribe (sorry) was that the internal fan does not blast away when the ambient temperature is closer to to the setting made in the cabin, say 25 or 26C ambient v 21 or 22C in the set in the cabin.
So when Sloppysod (I don't believe that) says after a regas that the air con behaves differently I would guess that it no longer needs to blast away because the incoming air is now colder and will bring the cabin temperature down at a lower fan speed.
Just my take and thanks again for the words of explanation about operating the recirculation.

Andy.

[GiveMeABreak]

No worries, but obviously the colder the air, the quicker it reaches requested temperature. They do say somewhere that shoving the fan on full serves no purpose in any attempt to cool the vehicle quicker - and that setting it on Auto will allow it to get to the desired temperature withing the capacity of the system to do so.

[Sloppysod]

Thanks Marc, for yet another great explanation on how the climate control works and from where it gets its data from........had to read it twice!!
Anyway, I will follow your test example in your earlier post and try to record it exactly the same way you did to make a comparison, between your C5 & mine.........I am now waiting for the warm weather to return to the north and a new thermometer to arrive...............oh!.............along with the weekend I will post my results.
However, I think it yesterday afternoon it worked as expected......baffled

[Hell Razor5543]

It is a Citroen; they delight in baffling not only their owners but everybody else who has to work on them!