C5 - Why doesn't my A/C work?

[wurlycorner]

The A/C in the C5 doesn't work (didn't when I bought it). I was assuming low gas, but having now got my Lexia working, I thought I'd try and confirm that before taking it in for a top up...

I'm none the wiser.
Checking the config of the car shows that it knows it has air-con, but when I do a comms check of the ECU's to try and diagnose when the A/C is up to, it says no communication with the A/C ECU. I assume though that this is normal, because mine has the manual A/C rather than auto?

Anyway, elsewhere I checked some of the parameters;
This is with the A/C switch 'on' (as you can see in the background)



Nothing seems to change when I switch the A/C button on/off, although the light on the button does go on/off as it should.

Any ideas?

One other thing I note is that the external temperature readings are cobblers (they're >20^C all the time, even when it's freezing )
Looking at my electrical diagrams it seems that the external temperature sensor feeds into the passenger door control unit (for some reason? ) and then into the A/C system.
Checking in the BSI the passenger door unit is one of the things that shows as having a permanent communication error (although everything seems to work ok the door ).
Could that have anything to do with it?

[DickieG]

It may well be down on gas which may explain why on the third photo the cut off request is displaying "Yes" but before getting it re-gassed, have a look at the condenser for oily patches on it's surface when looking at it through the front grill (particularly in the lower corners), if it has any then it almost certainly has a leak.

Re the passenger door unit you mention bear in mind that on some cars Citroen refers to sides of the car as per LHD.

[Estately]

I think that the air con needs to be able to acquire the outside air temperature from the unit in the passenger door mirror, could be the wire has degraded with opening and shutting of the door. Maybe the mirror has received a hefty thump at some time and caused the sensor to fail.

Others will be more qualified to comment but the 1 bar air con circuit pressure sounds too low to me.

Regarding leaks you may find that some re gassers offer a no air con no fee service + if regassed an ultraviolet dye to check for leaks if it the pressure falls again.

[citroenxm]

Is 1 bar of pressure enough.. dont they need about 5 bar to function efficiently..??

[wurlycorner]

I'm quite sure 1 bar is nothing like enough, it will need to be much more than that.
As I say, from what I can see, the system is doing nothing, not even engaging.

Thanks for the feedback guys, I'll have a look into the external temp sensor then and once that's sorted, see about getting a re-gas and cross my fingers.

No signs of any leaks btw.

[citroenxm]

If you get it gassed up etc and it all mechically works and still not cold c5 heater flaps can be a pita and jam and not go fully cold..

[steelcityuk]

It's unwise to go on circuit pressure to determine the amount of charge, the pressure will vary too much depending on temperature which is why aircon systems are filled by weight. However you could get hold of a re-gas can and put a few extra psi in the system to see if it works but proceed with caution because you really don't know how much gas is in the system and whether the pressure sensor is working correctly.

Steve.