I had a code 00256 for ac pressure switch. So I ordered a new one and got the part put on and now I am getting same cold with lower limit not reached. Any advice? Still have hot air coming through the vents with 95 degree weather. Not fun
My first guess is that you have a leak. The condenser is the first place that I would check as it is the most exposed to the elements. I have owned five older vehicles that I have had to replace the condensers on in order to resolve refrigerant leaks.
The condensers on some of the VAG cars develop leaks at the top where the plastic air guides for the intake system attach.
I had a similar issue a couple of years ago on my S6 and my system held vacuum for over a half hour so I had it charged up with refrigerant that contained a dye. It blew cold air for about a week and then stopped
Below is a picture of the condenser taken with a UV light shining on the area of the leak. It is emanating from where the plastic tab on the air inlet overlaps it.
Below is a picture with the new condenser installed and those plastic tabs cut off.
It is also recommended that you change the drier as well.
Had same issue with sensor error. After refill in 2 days system get empty and error code about pressure sensor. There was no visible leak under UV light in all system, but after replacing condenser everything was OK