Picasso aircon noises

Post your Cit/Peu/Ren air conditioning queries or advice.

Moderator: RichardW

mnde
Posts: 41
Joined: 22 Jul 2019, 23:00
x 4

Re: Aircon noises

Post by mnde »

GiveMeABreak wrote:
09 Aug 2019, 10:02
Pop your VIN up and I'll take a look.
Thanks - PM sent.

Cheers,

Mark

User avatar
GiveMeABreak
Forum Admin Team
Posts: 20501
Joined: 15 Sep 2015, 19:38
x 2028

Re: Aircon noises

Post by GiveMeABreak »

Ok, so the sensor on the condenser is the actual A/C Fluid Pressure Sensor (High or Low Pressure).

A/C Fluid Pressure Safety
The status of the air conditioning high and low pressure safety is transmitted by the BSI via a linear pressure sensor.
The linear pressure sensor measures the pressure of the air conditioning fluid.
The reception of pressure information is carried out by the engine ECU through a wire link.
The engine ECU makes the following information available to the BSI on the CAN network:
  • Air conditioning compressor cut-off due to safety function; Air conditioning compressor cut-off due to risk of overheating
  • Coolant pressure; 0 to 3100 KPa
  • Validity
The BSI sends the information to the air conditioning ECU via the COMFORT VAN network.

High Pressure Safety
The high pressure cut-off threshold and the retriggering threshold depending also on engine speed, are:
Cut-off threshold > 27 bars (absolute)
Retriggering threshold < 20 bars (absolute) and < 5650 rpm engine speed

Low Pressure Safety
The low pressure cut-off threshold and the retriggering threshold depending also on engine speed, are:
Cut-off threshold less than or equal to 2.5 bars (absolute)
Re-triggering threshold greater than or equal to 3 bars (absolute) and engine speed < 6250 rpm

mnde
Posts: 41
Joined: 22 Jul 2019, 23:00
x 4

Re: Aircon noises

Post by mnde »

That's fantastic info, thank you!

I'd better take the connector off this switch and see if there's engine oil in there. If the ECU is getting a misreading from the sensor... well I don't know, I just need to check it. And the connections on the compressor itself if I can get to them easily. Like i said, I'm suspicious that this started since I had oil contamination elsewhere in the main harness.

Thanks again,

Mark

mnde
Posts: 41
Joined: 22 Jul 2019, 23:00
x 4

Re: Aircon noises

Post by mnde »

I had some time earlier to take a look. I found both the compressor coil and AC pressure switch plugs and sockets looked clean, but I gave them a blast of contact cleaner anyway. I removed what looked like an earth plug from the block near the power steering pump and cleaned that up too. I cleaned out some more residual oil from the centre ECU plug and socket, and for good measure I cleaned up the other 2 plugs and sockets even though they looked clean. I checked inside the fuse box - all the connections in there looked clean.

Anyway this seems to have some the trick as the AC slipping/whirring/whooshing noises are greatly reduced. I tested engaging it at speed while driving, and at increased revs in neutral. Definitely seems better. Touch wood!

Cheers,

Mark

mnde
Posts: 41
Joined: 22 Jul 2019, 23:00
x 4

Re: Aircon noises

Post by mnde »

Hmm noises have returned on and off. Admins: please can you move this thread into the French aircon forum? I didn't see this when I first started it. Thanks!

mnde
Posts: 41
Joined: 22 Jul 2019, 23:00
x 4

Re: Picasso aircon noises

Post by mnde »

These noises have returned with the higher ambient temperatures. Can I check one thing: what is the correct behaviour of the cooling fan at idle with the AC engaged and the temp dial set on full cold?

I expected to see the fan on constantly, but instead it was cycling on and off. I can check again but I don't think I heard the compressor clutch disengage and re-engage while I was watching the fan.

When I turned the AC off, the fan stopped and remained off. Presumably as coolant temp was not quite high enough to trigger it.

I'm wondering if the compressor is being worked overtime... The temperature seems to be cool enough at the vents, it's just noisy... I can't hear the noise when I'm looking under the bonnet - but also I can't rev the engine and look at the same time...

mnde
Posts: 41
Joined: 22 Jul 2019, 23:00
x 4

Re: Picasso aircon noises

Post by mnde »

I ought to say: in February I had the clutch (transmission) replaced which bought on a return of the oil contamination issues caused by last year's oil pressure switch leak - hesitation, noisy exhaust, engine light with O2 sensor codes. The ECU had to be removed from its cradle and moved to one side to access the gearbox bolts. I guess that residual oil in the unit and plug wiring had migrated by the movement of the ECU and wiring being tilted and taped out of the way in the inner wing area.

I should have suspected straight away when the EML came on during the first test drive, but a new cat had been fitted at the same time as the clutch, so I thought it was to do with that. But I checked the ECU centre plug and found oil in there. After I'd removed this all the symptoms went away instantly.

I'm still wondering whether the AC noises are linked with this :( I cleaned out more residual oil from the centre ECU plug and socket a couple of weeks ago but the noises have remained. I've not yet checked the coolant sensor plug...

User avatar
EDC5
Donor 2020
Posts: 1194
Joined: 01 Jul 2017, 21:48
x 98

Re: Picasso aircon noises

Post by EDC5 »

I honestly wouldn't worry too much about the AC noises.

I get a momentary grinding noise /vibration from the compressor when the clutch engages and a hissing/whooshing noise from behind the dash when the car starts. I'm perfectly happy with the whooshing and hissing as it will be the sound of the first tranche of liquid refrigerant vaporising in the tube leading to the evaporator. It clears once this tube is cold enough to allow the metered liquid refrigerant to make it to the actual evaporator proper before evaporating.
As for the grinding noise/judder, well I'm just ignoring that as it still blows ice cold so there can't be too much wrong with it!

mnde
Posts: 41
Joined: 22 Jul 2019, 23:00
x 4

Re: Picasso aircon noises

Post by mnde »

Thanks - I'm not worried about the hissing and whooshing noises now - I accept that these are normal. It's the constant whining sound when the AC is engaged, like a motor, which varies up and down in pitch and intensity with engine revolutions. There's also a metallic vibrating sound, like a spring vibrating against itself if that makes sense.

I don't want to go to the expense of having the compressor replaced, only to find that the noises were being caused by something else like an electrical fault.

mnde
Posts: 41
Joined: 22 Jul 2019, 23:00
x 4

Re: Picasso aircon noises

Post by mnde »

I've made a video of the sound - it's plainly audible at the centre vents. After a few seconds I'm pressing the accelerator gently with AC engaged and blower set to 1 (so you can hear the noise better). This noise goes away instantly upon turning AC off.


User avatar
EDC5
Donor 2020
Posts: 1194
Joined: 01 Jul 2017, 21:48
x 98

Re: Picasso aircon noises

Post by EDC5 »

Those certainly are interensting noises from the vents. If the compressor was on the way out though I doubt if you would hear it inside the cabin.

I take it there are no such sounds when the AC is off?

I'm quite interested to hear the noise from under the bonnet when you do the same thing to confirm it's coming from the compressor.

mnde
Posts: 41
Joined: 22 Jul 2019, 23:00
x 4

Re: Picasso aircon noises

Post by mnde »

Yep, no such sounds with the AC off. I did kneel down and tried listening to/looking at the compressor while pressing the accelerator with my hand. Difficult to tell but I don't think I could hear a similar noise. Although it may just sound more concentrated/isolated at the air vent (kind of like a listening tube). I'll try and get a video soon. It was 9pm so I had to stop for the neighbours.

mnde
Posts: 41
Joined: 22 Jul 2019, 23:00
x 4

Re: Picasso aircon noises

Post by mnde »

I'm now wondering if I've got a blocked/stuck expansion valve and whether I've caused this.

After several weeks of lockdown without driving anywhere, I decided to start the engine and get the car up to temperature. I also ran the air-conditioning on full blast with fan on full speed to give it some exercise. After that I didn't use the car for another couple of weeks.

The first time I had to drive anywhere, the AC made loud noises as in the video, varying with engine speed, and the air smelt bad. I ran for a while with the AC on but heater on full, and eventually after a few more drives the smells went away.

I checked the pollen filter - it was dry, clean and didn't smell. It was only replaced in March, just before lockdown.

Did I unwittingly block/seize up the expansion valve by running the AC on full cold, full fan then switch off and not use the car again for a couple of weeks?

The reason I think the expansion valve may be at fault is that:
- the hissing through the valve, as heard through the vents is almost constant
- the compressor seems to be running constantly when AC is engaged, whatever the temp dial is set to
- I attribute the whirring noises to the compressor attempting to pump liquid refrigerant... (or the compressor is on the way out)
- the engine seems to lack power uphill when AC is engaged
- the AC goes cold, but not as cold as it should I think, and possibly fluctuates - hard to tell. I should use my laser thermometer on it...

What do you think? I'm going to have to get it checked out, and avoid using the AC when I need to use my car, which isn't a lot at the moment.

Cheers,

Mark