Suspected aircon problem - 2016 Allroad BiTDI

[muddyboots]

Hi all

Car is a 2016 A6 Allroad with ~50k miles.

I've noticed recently that my windscreen is fogging up frequently, and taking a lot of work to clear again.
With AC mode set to "Intensive" and fans up full, it still takes ages to clear the screen.

There's an obvious hiss that comes/goes when I turn the aircon on/off, and when temp is set to minimum the air doesn't feel as cold as I'd hope (although outside air is fairly cool anyway).

So I'm suspecting my aircon isn't working.

I'm booking in for a regas - but are there any common failures/faults to be looking for ?
I've seen various references to sensor replacement, but I'm not sure which sensor, and where these would be located on my car.

I've scanned with VCDS and no errors stored.
And the fact the hiss comes/goes as I turn the AC on/off makes me hopeful the compressor is operating.

Any thoughts welcome!

[bluezie]

When mine failed summer before last, the passenger side went warm first, and as more gas leaked, then both sides went warm. When it was low on gas, it made far more hissing and gurgling noises than normal.
I just used STP re-gas from Halfords, as I didn't want to spend loads having it properly re-gassed and it just to leak away. The first STP re-gas lasted 2 weeks, and the second 18 months and still going strong! :) So the leak sealant in the STP worked eventually.

BTW VCDS showed no fault codes when it was out of gas.

[Waddie]

Any loss of gas is usually accompanied by a loss of oil. Systems should be evacuated so that the correct amout of oil and gas can be added. Not to do so and you are risking a lot!

[muddyboots]

Interesting Bluezie, thanks.
Mine seems to be going exactly the same way. When the LHS side of my screen was fogging more than the RHS on a recent trip in horrendously wet weather, I initially put it down to my passenger who was talking incessantly and generating more moist air on that side...but maybe it's just going the same way as yours has.

Mine seems to use the newer R1234yf gas type, which seems to be a lot more expensive than the older R134a :(

I've read in numerous places that it leaks a lot faster than the older type too.
According to a page on HonestJohn:

R1234YF is flammable, is prone to leaking and costs four times as much. I'm getting a lot of reports of premature leakage of R1234YF, typically more than 75% by 2 years old.

Great!