C5 X7 - blower running but no air from vents after long drive

[bhc_comp]

Hi everyone,

I have an intermittent HVAC issue with my Citroen C5 X7 and haven't been able to find another thread describing exactly the same symptoms.

After a longer drive, the airflow from the vents sometimes becomes extremely weak or disappears almost completely. The strange part is that the blower itself is definitely still running. I can clearly hear it somewhere behind/inside the dashboard, and changing the fan speed also changes the sound of the blower, but almost no air comes out of the vents. Normally everything works perfectly again, so the problem is intermittent and seems to appear only after the car has been driven for some time.

My first thought was that one of the air distribution flaps or flap actuators might occasionally get stuck and block or redirect the airflow. I understand the C5 X7 has several motorised HVAC flaps. I have already tried changing the airflow direction between the footwell, dashboard vents and windscreen while the problem is happening, but it makes no difference. I also tried the windscreen demist/defrost button, which immediately commands maximum blower speed. I can clearly hear the blower ramp up to full speed, but there is still almost no airflow from any of the vents. I have also tried completely switching off the climate control and ventilation while driving, leaving it off for around five minutes and then switching it back on, but the airflow does not return.

However, if I park the car and leave it for some time, the system works normally again afterwards. During shorter/city driving, everything works without any problem. The issue seems to appear mainly after longer drives.

Because the blower itself clearly continues running, and changing the distribution settings does not restore airflow, I am wondering whether there could be a flap that intermittently blocks the airflow completely, or whether something else inside the HVAC unit could be restricting the airflow after prolonged use.

Has anyone experienced this behaviour on a C5 X7? I would especially be interested to know whether this points more towards a flap/actuator problem, evaporator icing, or another known fault on these cars.

[xantia_v6]

Is it perhaps the A/C evaporator freezing up and blocking the airflow with ice?

That would typically be caused by the system being low on refrigerant although other faults could also cause it..

[Paul-R]

Have you checked/replaced the pollen filter?

[bhc_comp]

Is it perhaps the A/C evaporator freezing up and blocking the airflow with ice?

That would typically be caused by the system being low on refrigerant although other faults could also cause it..

Evaporator icing sounds like a quite realistic scenario to me as well, especially because the blower continues to run normally while the airflow almost disappears, and the system works again after the car has been parked for a while.

Is there a good way to confirm evaporator icing on the C5 X7, for example through Lexia/Diagbox by monitoring the evaporator temperature sensor or refrigerant pressure while the problem is happening?

Have you checked/replaced the pollen filter?

Hey Paul, the pollen filter was replaced relatively recently, but I will check it again just to rule it out. Why do you think the pollen filter would cause such issues?

One additional detail that may or may not be related: on very hot days, usually when the outside temperature display is around 38°C or higher, the A/C compressor also tends to switch off during city driving. This happens faster if the car has been parked in direct sun, while on the open road it does not seem to happen at all.

I had assumed this might be a separate issue, possibly related to condenser cooling/high refrigerant pressure, but I thought it might be worth mentioning in case the two symptoms could somehow be related.

[mickthemaverick]

I don't know if this is relevant or just coincidence but about 4 weeks ago I was driving to a special birthday lunch on one of the very hot days. The aircon began as normal but after maybe 7 or 8 miles it started to feel warmer, a couple more miles and the airflow started dropping off. By the time we got to the venue it was a very weak blow and only a tad colder than ambient. We went in for lunch having left the car in the sun. When we returned we had to open all the doors to get some heat out before getting in and starting. The aircon came on more or less as normal but the drive home yielded a similar pattern.

Due to my current lack of stamina I booked it in to the main dealer for an aircon service. An appointment was made and they carried out the complete service while I waited. They reported back, they had extracted 135g, pulled a perfect vacuum held for 30 minutes, refilled with 435g of R134a as is its capacity. It is now ice cold regardless of outside temperatures and only cost £149.00 for the refrigerant and 1.75 hrs labour.

Maybe your refrigerant level is low, causing low pressure in the system and thus easier freezing?

[windy1603]

I had a similar issue on my 308 with evaporator icing (due to a blocked heater matrix and not enough heat in the heater box i think) I diagnosed it by turnin A/C off but left set on 16 Deg over about 5-10 mins the blower air started to get warmer and airflow increased. Switch A/C back on and 10-20 mins later airflow would drop off again

[xantia_v6]

To properly diagnose evaporator icing, you really need to get refrigeration gauges connected and check that the low pressure line has a pressure which indicates an evaporation temperature above freezing. The built in sensors cannot do this.

[bhc_comp]

Thanks, everyone. This is very useful....

I previously tried switching the whole climate system off for around 5-10 minutes, but I did not leave the blower running. Next time the issue happens I will try switching only the A/C compressor off while keeping the blower running at a fairly high speed for 10-15 minutes and see if the airflow would return. That should hopefully give a better indication whether the evaporator is actually icing up.

I will also ask the A/C technician to check the system with proper gauges and monitor the low-side pressure while the fault is occurring, rather than relying only on Diagbox.

One thing worth mentioning is that the refrigerant has been checked/refilled previously while investigating a separate A/C issue, so I am not sure that low refrigerant is the cause. However, I understand that this does not necessarily rule out evaporator icing caused by another fault.

I’ll report back once I’ve had a chance to test it properly.

[RichardW]

Pretty sure you will find this is the evap icing up. Our Mk 1 C4 Pic used to do this; never got to the bottom of why. If you turn the AC off and keep driving the air flow should return in 5-10 mins. There was another recent thread about this. The Evap temp sensor should cycle the compressor when approaching the icing point; ours looked to be giving a reasonable reading, but I wondered if it had in fact got dislodged and was reading air temp rather than evap surface temp.