C3 2008 a/c cold'ish one vent only

[Alexr354]

Hi have a petrol 1.4 c3 rythem 2008.

Had the car for a year the a/c was sort of working last summer. But if you turned blower upto 4 it would start coming out normal temp on 3 it would work.
This year during hot weather went to use again
Only one dash vent comes out slightly cold (not fully chilled) the 3 others blow normal air you would expect with temp setting to cold but a/c not on. All other vents in any direction (foot, windscreen) blow non-ac air. Temp gauge works fine between hot and cold normal air.

The system is pressurised I have checked that with a gauge and well in green section. Condenser can be heard clicking in when a/c button pressed and electric fan behind the radiator kicks in.

Any ideas?
Is there a flap between chilled a/c air input and normal air that could be stuck. The fact one vent starts to get slightly colder makes me think if there must be a flap between normal air and a/c air

[ozvtr]

If you can select 'hot' and the air gets hot and then select 'cool' and the air gets cool, then the mixer flap is working. If you get the same temp then there is a problem.
Do you have auto climate control or knobs?
Next thing is to get a set of service gauges on the on the A/C service ports and see what the pressures are with the compressor running. I assume the gage you are using is one attached to a filler bottle? It's not good enough for fault finding. However for poop and laughter, with your gauge attached to the low pressure port (the smaller port)and the compressor running, that gauge should show 'about' halfway between '0' and the green section. The closer to the green section the needle gets, the poorer the performance of the system.
It sounds like a compressor problem but without those pressures, I couldn't say.