Mystery problem with intermittent AC

[Vandeo]

Please, I am desperate!
Ok. So I cant find a problem with digital dual zone AC in car. LANCIA MUSA.
I noticed that ac is shutting off after several minutes of working fine.
It was all topped with gas.
First, I replaced preasuure switch (linear), no change.
Second, I noticed that second speed of ventilator is not turning on always when ac is on, and replaced the reostat .
Third, condenser was all in pieces, so I replaced it, along with drier.
Fourth, checked flaps in air vent and all flaps blow as it should and allow cold or hot air as it should, and while checking, again checked gas and preassure, on 42oC outside, low preassure was 3 nad high on 16 on idle and AC works fine.

On 3000 RPM high preassure was on 21 and low arround 6 and after several seconds on 3000 RPM, ac stops blowing cold, and few minutes past, starts blowing colds agin. Then after few more minutes again stops with cold air. Cold , not cold happends few more times and after that no more cold. When stops blowing cold, compresor and second speed of vent turns off.

[tbirdtbird]

Some of your info is not clear but a bit rambling. How many miles on the car please.
What units are your pressures, they are not familiar. Bar? We are in the USA.
Despite the confusion, I would have to suspect the clutch gap of the compressor. When the AC cycles off open the hood and see if the comp is actually spinning. (not just the outer pulley, it spins all the time)
Gap s/b .020 and is adjustable

[Vandeo]

Thank You for reply. Yes, it should say BAR (not PSI) regarding pressure.
Gas is charged exactly 500 grams, by the book.
The engaging system on compressor is working fine (when the compressor works, an then shuts of (clutch returns in previous position))
Could it be that expansion valve or car digital AC panel are causing the problem ?

[Cusser]

The engaging system on compressor is working fine (when the compressor works, an then shuts of (clutch returns in previous position))

THIS is why tbirdtbird suggested to check the AC clutch air gap !!!

I had to remove a shim from the AC clutch on my Frontier to fix it back in 2019.

[tbirdtbird]

Please re-read my answer on how to determine if the clutch gap is out of spec. This can even happen on a brand new comp.
If the spinning (driving) hub is too far away from the driven hub of the comp, then as the parts heat up, there isn’t enough magnetism to engage the compressor drive shaft, and intermittent compressor action will be noted. Be careful working around moving parts. This gap is checked and with the engine off, using standard feeler gauges. The gap is adjustable easily. Perhaps locating a you tube video would help you to understand this better.
While there could be another explanation, checking the gap is the first step. Measure the gap and report back. Right now you are not following the required diagnostic steps.
Remember, a proper diagnosis means the problem is half solved.

[JohnHere]

Third, condenser was all in pieces, so I replaced it, along with drier.

What do you mean by that?

Do you have the precise amount (by weight) of refrigerant in the system according to the manufacturer's specifications?

What year is your Lancia?

[tbirdtbird]

Wow, John, I missed that!

[event3horizon]

His pressures at 3k rpm translate to 87 PSI low and 305 PSI high. That's pretty bad. Could the clutch gap thing cause these high pressures or is this an obvious blockage in the system?

[JohnHere]

Earlier, the reason I asked about the model year was to try to determine whether this vehicle has a fixed-displacement or variable-displacement compressor. If the latter, the compressor could be stuck at maximum displacement, potentially causing the high pressures. But the OP hasn't returned.