calm_your_ham

Only thing that did concern me was the new sensor having no sort of serial number or writing on it, it was just blank. It came in a Mahle box but obviously that’s easily done. I just didn’t think much of it until now seeing as the sensor change had altered something and was then working.

Hi Gareth, It was a MAHLE brand sensor 🙂 The exact website I bought the part from was OnlineCarParts and I didn’t know they were an AutoDoc “reseller” from what I know, only found out when I got the shipping details saying it was coming from AutoDoc. Didn’t really concern me that shipping was £8

Hi all, I’m hoping to get some insight on an issue I’m having and if anyone else has had the same/similar. So I bought my A4 B8 in May 2025 and the car was sold with the A/C not working. The button would work as if the A/C had no issues, staying on when pressed, etc. I had the system checked by Halfords who told me that the system had about 450 grams of gas in it and held pressure so they only topped it up 100 grams, but didn’t empty the system out and so on, just recommended replacing the condenser unit which I didn’t do after they quoted me £400. Fast forward to 25°C heats in June in Scotland and I thought I should get around to fixing it. I looked up the codes I got and looked through some forums and it all pointed to the infamous pressure sensor issue. I ordered the new sensor from Autodoc, replaced it, A/C still didn’t work but this time the button would only stay lit up when I held it, turning off as soon as I let go. One thing to note is when replacing the sensor, I didn’t get the little squirt of gas that everyone mentions. Eventually I dropped the car off with a mechanic who did a proper recharge, pulling out 70 grams, doing a leak and pressure test and filling it up with 550 grams. The system supposedly held pressure for 20 minutes and the A/C finally worked as it should. A week later, I was out with friends, A/C working fine, then overnight it was no longer working in the morning, but the button stays lit up like it did at first. So 2 days ago I left the car at the same mechanic who tested the system again and have now said that there is a leak in the system, but they did a bubble test and cannot find the leak anywhere and want to do a further investigation. Just wondering if anyone has any ideas or had the same issue? I don’t know if they tested the sensor for leaks (I’ve seen a couple forums where that was the issue) but where could I be looking next? The car is throwing up the same codes about the lower limit being exceeded and “No Signal/Communication” with sensor. Could it be the sensor has failed again for some reason and leaked all the gas? TIA everyone