AC randomly not cooling?

[Thor]

So I've been on a trip this weekend, first time driving the van in summer heat (20-25c). Sometimes the AC works really well so it should not need refilling, and sometimes it just doesn't seem to want to cool at all and the van starts getting too hot inside. When it cools it also turns the fan up a little. I cant find any rhyme or reason to it, but if I turn it off for a few minutes it sometimes starts cooling a few minutes after I turn it on again.

Anyone have any ideas? 300km left today and it's getting hotter...

 

[DXX]

Without a bulkhead it’s a large volume to cool. I tend to use re-circulate most of the time, it helps the load on the AC and prevents most of the road exhaust nasties entering the cab. The ‘pollen’ filter only takes out the particulates not the noxious gases.

 

[Thor]

Without a bulkhead it’s a large volume to cool. I tend to use re-circulate most of the time, it helps the load on the AC and prevents most of the road exhaust nasties entering the cab. The ‘pollen’ filter only takes out the particulates not the noxious gases.

Seems I was unclear: the issue is not that the AC can't keep the van cool, it's that a lot of the time it's not even trying. It's a van with bulkhead behind the front seats, and it gets freezing cold when the AC wants to work. When it's not cooling recirculation makes it hotter than not, as the cab quickely gets hotter than outside air.

 

[Ads_Essex]

Would this be a sign it’s lost pressure, so the motor can’t always function?

 

[Thor]

Would this be a sign it’s lost pressure, so the motor can’t always function?

I've had cars before where the refrigerant has leaked out, and they just cool less over time until they don't cool at all. The van sometimes cools really well, indicating that the refrigerant is fine.

 

[mmi]

Just to understand better - it happens when the knobs are exactly as in your picture?
Because setting airflow direction control (right knob) to 12 o'clock turns on windscreen defrosting (=hot air).

When it cools it also turns the fan up a little.

More likely automatic recirculation as the AC unit (in the picture) can't control blower speed, instead turns on air recirculation (see the data extract below).
Does the engine idle on slightly increased revs (almost 1000 rpm) when set at Max cold? Does the engine coolant fan run?

The van sometimes cools really well, indicating that the refrigerant is fine.

Still, when it was serviced (refrigerant refill) last time?

 

[Thor]

Just to understand better - it happens when the knobs are exactly as in your picture?
Beacause setting airflow direction control (right knob) to 12 o'clock turns on windscreen defrosting (=hot air).

The settings in the picture is my preferred, but i have tried pretty much every other combination of settings i can think off with no change. I don't think the defroster vents blow hot when AC is on from my testing, feels like the same air temp as everything else.

More likely automatic recirculation as the AC unit (in the picture) can't control blower speed, instead turns on air recirculation (see the data extract below).
Does the engine idle on slightly increased revs (almost 1000 rpm) when set at Max cold? Does the engine coolant fan run?

I'll need to test that, I've mostly been experimenting while driving.

It's had regular service, no idea if AC has been serviced specifically. I will have it checked, but I'd rather try everything else before spending the money. I'm just finding it weird that it sometimes cools really well, and sometimes just not seems to try at all.

 

[JJ1]

I found this on my 2017 T6.

My theory is that the ac rad in the heater matrix freezes solid and can’t pass air through. I knock the AC off for a while and the air flow starts again.

The fans never change speed.

My theory also backed up by seeing the pipe across the engineer bay having a lot of frost on it when the AC has been on for a while.

Pretty sure that’s how it’s always been from the factory. It might suggest there is an issue with the expansion valve on the AC system. I’m not a refrigeration engineer but I’m not sure what else would cause that.