Citroen C4 GP 2015 - heater matrix issue?

[qwertyqaz]

Hi!

I have a Citroen C4 Grand Picasso from 2015 in diesel, left hand steering. Last summer, I noticed that the AC is not as efficient as it used to be. First I thought that it just needs a service but then I noticed that passenger's side is getting a lot warmer air than the driver's side. Since the summer was not super hot where I live, I did nothing about it.

Now that it is winter, I realised that the passenger's side is not getting hot air. The car has a dual heating/cooling system (I mean separate control for each side). The things I noticed:

• Driver's side is getting warm air while passenger's side is barely warm or just cold

• The passenger's side of the center console get slightly warm air while the air coming from the vent by the window seems just cold

• It seems to me that the passenger's side vents blow less air than the driver's side vents

• When I close all vents, then open the passenger's window vent and then open and close one of the driver's side vents, I can feel that there is more/less air coming from the vent and also the temperature seems to get a bit higher when I close the driver's side vent

• The back row's vents are blowing warm air

• After one of the yearly services, I noticed that there was a bit of a whistling noise every time I would turn on the heating/cooling, I thought that maybe it was due to incorrectly placed cabin filter but this persisted after the next replacement (assuming the workshop really did replace the filters)

Considering all of the above, do you think that this might be a faulty heater matrix? If it is clogged, would it affect both heating and AC? Considering that I have a left hand drive car, how difficult would the replacement be if I would want to do it myself? Could it be the flaps and not the matrix or something completely different?


Thank you!

[RichardW]

The matrix blocking up is a common problem, and will almost certainly account for the lack of heat on the right hand side. There may be other issues accounting for lack of flow, but you probably need to fix the matrix first. Here in the UK, it's a relatively easy job from the passenger foot well (but changing the pollen filter is tough!), but more trick on a LHD car - I think you will have to remove the steering column. The hardest part seemingly is getting the pipe clamps back on and sealed.

[PaulC5]

Possibilities include the warm air flap not moving enough, not enough refrigerant so not cooling much (at 11 years old probable), the heater matrix blocked. You might have all three of these.

[qwertyqaz]

Thank you for your replies. Do you know if the air flaps would also be on the driver's side in a LHD car? I have a diagbox that I believe I can use to test different flaps.

I think the next step will be to get a new heater matrix. I saw a video where the steering column was removed. It looked easy, just couple of screws. Is any calibration needed afterwards? Based on the video I would think that it should be enough to just put it back in place.

Do you know what the correct pressure in the aircon system is? I saw that it was increasing when I activated aircon while having the diagbox hooked up to the car.

[PaulC5]

If you have separate temperature controls for both sides of the car there will also be separate flaps.

[qwertyqaz]

I finally begun looking into those issues. I got a new heater matrix that I am planning to replace tomorrow. I decided to start by fully draining the coolant and flushing the system with distilled water. Based on what I read, I understood that I would need about 6-7 liters of new coolant. The thing is that when I drained the system, I got maybe 2-3 liters out. What I did was to open the coolant tank and then I removed the radiator hose under the car. I saw one video showing this process. What am I missing? Why can't I get the full 6 liters out? Are there any other hoses I need to disconnect? I saw a video about an older C4 in italian where they also pushed the coolant out with pressurised air through the coolant container. ChatGPT was suggesting draining the engine block but I cannot understand how I could do that.

I removed some panelling and run an actuator test for the aircon mixing system and the actuator is moving. Can it still be an issue with the flap even if I can see the actuator moving? What makes me think that it is not the heater matrix or at least not only the heater matrix, is that I get weaker air flow on the passanger's side and the air is also cooler in the winter and warmer in the summer.

[PaulC5]

All the rest of the coolant will be in the engine block and heater matrix. Since it is not easy to remove this it is best to fill up with 100% strength coolant by the right amount to give about 50% strength and then do any final topping up using water.

[admiral51]

My 2010 C4 2.0HDI had issues with not getting hot air in the cabin, warm yes but definitely not hot. I had the heater Matrix changed last year and to be honest it was better but not as hot as i expected to be.
Last week it decided to throw coolant out from the thermostat housing, currently still in the garage awaiting repair as they were busy and i dont need it for another week.
From what i have been told the thermostat is electronically controlled so fingers crossed when i get it back it will give me the hot air requested on high.
Air flow was not an issue, just that the temperature was luke warm. Mine is a RHD and i found that temperature was warmer on the passenger side ( Driver side LHD ) until i had the matrix changed.

Colin