A\C Citroen C4 GP

[Trafic2011]

Hello,
I have the following air conditioning problem on a 2007 Citroen C4 Grand Picasso.
The air conditioner control module next to the driver's seat works with all its buttons (fan levels +-, rear window heating), absolutely everything works, except for the A/C button, the LED lights up, but I can't start and stop the air conditioner. The compressor starts automatically every time the engine is started, but I cannot control it from the unit using the A/C button.
Has there been any similar case for which there is any solution? Thanks.

[GiveMeABreak]

I've uploaded your pictures to the Forum (just use the full editor button to attach pictures) in case the third party hosting site goes down in future.

There are 2 possibilities I can think of:

1) The Compressor may start up initially, but may stop running a few minutes or less after startup. This can be caused by low gas. As far as the AC control panel is concerned the A/C light will still show green, but you may not be getting any cooling and the compressor may stop running. This is a safety measure to prevent compressor damage.

2) If the A/C continues to blow ice cold air in the cabin when on low and carries on working, then you can rule that out. You may have a faulty A/C ECU.

The A/C ECU is a unit into which both the driver and passenger A/C control panels plug into. These can become faulty over time. I had a member a few days ago with a problem concerning fading lights on his panel. He replaced the AC/Unit which is quite easy to access and has solved his issue.

Ideally it would need a diagnostic to see if there is any fault code, but in the other case it fixed the issue. Here's a link to that post:

viewtopic.php?t=73932

[Trafic2011]

Thanks for the reply.
Yesterday we filled up the freon system in a service center. There are no mechanical problems with the system. Everything works great. The control by the driver's door also works well with all its buttons, only the AC on/off button does not function properly.
On diagnostics, the car shows no errors related to the air conditioning system. Many diagnostics of the car have been done in different auto repair shops. The problem only persists with the A/C/compressor on/off. Everything else works without a problem.
The compressor runs continuously both at low and high speeds without being able to shut off after starting the engine. I will look at the control unit for the air conditioner (A/C ECU) Hopefully the problem turns out to be from it and everything works as before.

Thanks.

[GiveMeABreak]

Ok, please update us, as it's always useful for others with similar problems.

[Trafic2011]

This is strange, there is no such module behind the glove box of the car. There are also no cables that reach the specified location. Only one that I have photographed, but I guess that apparently such a module is not intended for all Citroen C4 Grand Picasso models 2006-2013. Diagnostics does not detect AC/Ecu, I don't have any cables to power such a module there. This is very strange indeed. Can someone explain if each such module is mandatory, given that my car has air conditioning, not climate tronic.

[GiveMeABreak]

It depends on your vehicle's options. If you pop your VIN up I can see what system you have (please post your VIN in full without spaces - it will be automatically masked from public view after submitting your post & will only be visible to staff).

[Trafic2011]

VF7**************[VIN obfuscated, can be read by forum staff]

[GiveMeABreak]

Ok, so that confirms you have the 'Single Air Conditioning' system fitted. So you don't have this additional module which is only for models with 'Automatic Air Conditioning'.

SO your best bet is to try and get the vehicle diagnosed. The functions for these units are managed inside the side control panels, but I would certainly want to get a diagnostic done before replacing them, unless you have a cheap used one you can try.

[Trafic2011]

Ok, so that confirms you have the 'Single Air Conditioning' system fitted. So you don't have this additional module which is only for models with 'Automatic Air Conditioning'.

SO your best bet is to try and get the vehicle diagnosed. The functions for these units are managed inside the side control panels, but I would certainly want to get a diagnostic done before replacing them, unless you have a cheap used one you can try.

On diagnostics at a PSA service, they did not find a problem with the air conditioning system.
I have replaced it with another module - second hand, again the problem is on the face, after checking that there is no broken cable anywhere.
The problem is very strange and I have no explanation for it.