Citroen DS3 air conditioning problems

[Mikhail]

Hi, all!

If anyone could advise me on this issue that would be much appreciated. I love this car, but it is trying to bankrupt me right now!

Anyways, my current problem:

I've noticed that my air conditioning only works if I set the fan speed to the highest setting, or the one just below that (8/8 or 7/8). I've got the model with the automatic climate control, btw. It doesn't make a difference what the heat is set to. I can see the aircon clutch engage if the fans are high, and not engage otherwise. The fan speeds all seem to work, as in the fan speed changes depending on the setting. I've just had it regassed, and it blows nice and cold when the aircon clutch does engage. It keeps running as long as the fans are high, but it's like being in a wind tunnel. If it's running on high, and I turn the fan speed down, the aircon clutch disengages.

Now, sometime last year I replaced the blower control module with a cheap one from Amazon. Is it possible that this is the problem?

Many thanks in advance!

[GiveMeABreak]

Although cheap aftermarket blower motor control modules are generally cheap for a reason and are known not to work at all, this shouldn't affect whether the A/C compressor is engaging or not. This module just controls the fan speed and nothing else. When it fails, it usually results in the fan being stuck on high speed all the time.

Pop your VIN ups so I can see which system you have.

[Mikhail]

Many thanks for taking the time to reply. It does seem like a pretty strange fault.

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

[GiveMeABreak]

So you have the Automatic Air Conditioning system fitted. Your vehicle also has a clutchless compressor. So even when the A/C is not activated, the accessory belt still drives the compressor. So the pulley on the compressor does not have a clutch.

These are the main conditions where the A/C compressor is cut off:

Air conditioning fluid pressure safety
Air-conditioning compressor without clutch:

• When the pressure of the air conditioning fluid is below 2,5 bar, the air conditioning compressor is cut off
• The air conditioning compressor is triggered again when the air conditioning fluid pressure increases to above 2,8 bar
• When the pressure of the air conditioning fluid is greater than 28,2 bars, the air conditioning compressor is cut off
• The air conditioning compressor is reactivated when the refrigerant pressure falls below 20 bars
• The aircon compressor is effective for a minimum of 150 seconds

Air conditioning evaporator icing safety function
The BSI prohibits the activation of the air conditioning compressor in certain exterior temperature conditions to prevent icing up of the air conditioning evaporator. The evaporator icing up safety function is managed by the BSI:

• If the evaporator sensor temperature is below 1°C for 15 seconds, the air conditioning compressor is switched off
• The air conditioning compressor is reactivated if the temperature rises again to more than 3°C

Safety as a function of the electrical diagnosis
The air conditioning compressor is cut in the following conditions:

• Air conditioning compressor clutch fault
• Air conditioning compressor electrovalve fault
• Air conditioning fluid pressure sensor fault
• Air blower fault (delay of 30 seconds)
• Fault in communication between the engine ECU and the built-in systems interface
• Fault in communication between the engine fuse box and the built-in systems interface (BSI)

So the only area where the blower motor control module would affect the A/C cut off is in the last bullet list where I have highlighted in red.

So unless the system has another fault, it may be worth fitting a proper branded Blower Motor Control Module and see if that solves your problem.

[Mikhail]

Thanks again!

My aircon does seem to have a clutch, though. When the aircon comes on, the outer disc on the pulley snaps in with an audible clunk and then it blows cold. When the outer disc on the pulley wheel snaps out again, the aircon stops.

But that aside, I'm leaning towards the blower control module, too.

Thanks for confirming that this is at least a possibility!

[Mikhail]

...also, I just timed it, and it does seem to take 30 seconds from turning the fan speed down for the clutch to pop out again. Just ordered a new part - fingers crossed that it might actually be this simple!

I really appreciate you taking the time to help a stranger on the internet

[GiveMeABreak]

No problems, this is the A/C compressor without a clutch:

Key

(2) Compressor shaft.
(3) Oscillating plate.
(4) Piston.
(5) External control valve.
(6) No. cylinder.
(7) Clutchless pulley.
The clutchless pulley (7) is driven by the engine accessories belt.
When the air conditioning cuts in, the external control valve (5) permits modification of the pressure inside the body of the air conditioning compressor according to the temperature required by the passengers.
The modification of the pressure inside the compressor body has the effect of tilting the oscillating plate (3) so modifying the travel of the pistons (4).
The longer the travel of the pistons the greater the volume of fluid to be compressed, therefore the flow of refrigerant in the loop will increase in turn increasing the production of cold air.
When the air conditioning is switched off, the pressure inside the body of the air conditioning compressor is modified to allow the oscillating plate (3) to return to the position perpendicular to the air conditioning compressor shaft (2).

Note: When the oscillating plate (3) is perpendicular to the compressor shaft (2) the travel of the pistons (4) is equivalent to approximately 2% of the maximum capacity. When the air conditioning is not activated, the compressor continues to be driven by the ancillary drive belt.

[Mikhail]

That's actually pretty interesting - I didn't realise such a thing existed. Mine definitely does have a clutch, though. I tried to take a video of it engaging and disengaging on my phone, but it's too dark in there and I don't have a torch with me.

Although my aircon does have an automatic mode, it also has a manual mode with a switch labelled "A/C", that presumably is meant to engage the clutch when you press it. If it's on manual, high fan setting, it engages. If it's on auto, with a low temp setting that makes the fans roar in to quickly reach the set temp, it also engages. So the clutch only engages with high fan setting (either auto or manual) + the A/C button pressed. And if you leave the fans high, it keeps running.

So it certainly seems to be related to fan speed, and that 30 second delay in the system shutting down does ring true. I watched the clutch and timed it after turning the fans down, and sure enough, 30 seconds later it disengaged!

So yeah, new part ordered, and I'll report back if it works in the hopes that this thread might help someone else.

Wish me luck, and thanks again! It's actually made my day that someone I never met has made an effort to help me out today.

Have a good one!

[Mikhail]

I did manage to take a video in the end. Took 30 seconds from turning down the fan to the aircon cutting out again, but I shortened it because nobody wants to watch my drive belt spinning for that long!

[Mikhail]

...aaaaannddd...

Replacing the blower control module has fixed the problem!

Here's the part I used: https://www.autodoc.co.uk/mahle-original/15285498

Here's the YouTube video showing how to change it:

Hope this helps somebody else.

[GiveMeABreak]

Sorted, well done.

[Mikhail]

Thanks! It was a pain to diagnose - went down a rabbit hole with this the last few weeks. But such an easy fix once figured out. Thanks for helping - that thing about the 30 second delay was a great confirmation.

[freebie71]

I had exactly the same problem. Blower control module had packed up, changed it for a cheap eBay version. Blower worked again but aircon only kicked in when blower was on full. Saw this post, ordered a proper replacement, plugged it in and aircon now works fine on all blower settings! Thanks for this post! It was really doing my head in!

[GiveMeABreak]

Cheapo units are cheap for a reason.