AC problems

[Peter Palmer]

I know this is a long drawn out post so TLDR : aircon made weird noise now cycles on and off on its own.

I wonder if anyone can point to what is going on here, I have a 2020 Peugeot Expert 2.0 HDI and at first the air con was absolutely fine, last winter the van started making a kind of "hooting noise" periodically, I traced it to when the AC was switched on, it wasn't a slipping belt just a weird sort of brief noise maybe once or twice a day.

Fast forward to this summer and the AC didn't really work properly although it did work occasionally. Sometimes it took ages to get going, then it would work fine, then it wouldn't work at all for a bit. Now I do have the gauges and I've re-filled several vehicles in the past with that DIY gas you can get off E-bay and its always had excellent results every time I've done it. On our previous dispatch van after I changed the condenser I filled it to a static pressure of 90 PSI with a running pressure of 30/150 PSI and that worked brilliant for the next 4 years that we owned it so it must be somewhere near.

On this current van when I checked it it had a static pressure of 60 PSI and a running pressure of 15/100 which I thought was a little low (this is R410a so not the newer gas and the ambient temp was about the same as the first van 25 deg C or so) So I topped it up a little, not very much. I now have a static pressure of 90 again and a running pressure of 40/175) This should be well within the limits of the system I think.

It now gets cold quickly every time but what is happening now is the clutch is cycling on and off, maybe every 10 seconds or so, this is at idle, so on for 10 seconds then off for 10 seconds, this could well be normal operation but it seems to be doing it when you drive so cold air for 10 seconds then warm air for 10 seconds. Watching the gauges at idle they mimic the readings above so 40/175 for 10 seconds then 90/90 for 10 seconds then rinse and repeat. I've not heard the hooting noise for ages either.

I'm thinking its possibly a faulty pressure switch but what was the hooting I heard last winter? and lastly does anyone know if the pressure switch has a Schrader valve behind it on these systems as even the cheap DIY gas isn't that cheap.

[mickthemaverick]

TLDR?

[Paul-R]

Too long, didn't read.

[RichardW]

Is the radiator fan working?

[Peter Palmer]

Is the radiator fan working?

Not checked actually but does the radiator fan always run whilst the vehicle is in motion and the AC is on.

[RichardW]

It should do, but on these it may just run at full chat for a few seconds then off, then repeat. The squealing noise may have been the fan giving up - I had to replace one on our last C4 Picasso because of this. But once the van is moving it should give enough air flow to keep the pressure down; but if the feedback from the fan is wrong it may be upsetting the AC.

[Peter Palmer]

Good point, I'll look into it this weekend.

[Peter Palmer]

Had a quick look, fan seems to be running ok as soon as the AC is fired up. This is the system going on and off.



I've had a look with diagbox and the only anomaly I can find is with the various engine modules. This is the bit I don't get and I've had this problem before with other things - there are several ECU's listed under the engine section all with completely different names/codes. Not sure if all are present or you should pick the one that your vehicle has fitted, all except one of them give various readings on different stuff so if its not present it shouldn't show anything right? But 2 modules show the AC pressure as 12 bar or so and the other two show it as 0.6 bar which is very odd.







Maybe it is meant to work like that on idle I'm not really sure, need to go on a longish journey to see how it behaves, other than that we have another similar van with a leaking condenser so currently no gas, I'll nick the pressure sensor off that as I think its the same one, that will tell me if there is a Schrader valve under it for a start.

[Peter Palmer]

Think I've found the correct ECU



And that corelates to this in diagbox



This page (forgot to take picture) shows the AC "off" pressure as 8 bar which looks right if not a little high but only shows the "on" pressure as 9 bar, my gauges yesterday were showing it at least 12 bar, maybe that could be something?

[RichardW]

What is the evap temp sensor reading when it cycles on / off?

[Peter Palmer]

What is the evap temp sensor reading when it cycles on / off?

Just checked and it started at 22 which is what the outside temp was just about, once the AC kicked in it fell rapidly and the system switched off again, the lowest reading it got to was 0.3C Do you think that is what is switching it off as it thinks its too cold?

If the 0.3 reading is accurate what would cause it to go get that cold?

Edit : Just tried it with the cabin/pollen filter removed and it actually goes to -3.2 now before it switches off. Not sure what is going on.

[PaulC5]

The engine coolant temperature appears to be suggesting -267°C. I would have a look at this as it may be giving some problems. Could be a sensor fault or its wiring/connector.

[Peter Palmer]

Thats on the same engine module that shows the low ac pressure, on other modules both the ac pressure and coolant temp are fine.

I just cant fathom why diagbox lists several ecu's and furthermore why when you do select them they show what appears to be live data, surely only one ecu is fitted to the vehicle.

[RichardW]

The Comms protocols are probably different for the different ECUs so if you select the wrong one it is scrambling the data. If you were able to read OBD2 data it should give the real figures.

It looks like it is the evap sensor cycling the AC so that's probably normal, but is there a lack of air flow? Does the cycle time extend if you turn the fan up? It sounds like you have put in one of the replacement HC gasses? You may need to add a bit more to get the low side pressure and hence boiling point up a bit?