Air conditioning hissing


New member
My mk5 1.6 fsi has started making a hissing sound when I turn on the ac. The noise stops when I hit the ECON button.
I had read that if the refrigerant is low it can make that noise so I had the system cleaned and refilled, but a week later it has started making the noise again.
Could it be the Air Condition Pressure Switch Sensor? At the moment the air is still getting cooler.
Any help greatly appreciated


Drag Racing Champion
I have had funny noises coming from the Txv on a correctly charged system but it was more of a whistle noise that would come and go from the Txv valve. One day it just stopped never to come back. The pressure sensor just senses pressure does not have refrigerant flowing through it so it should not make any noises. Are you are only hearing this in the cabin & not engine bay?


Ready to race!
Mine did this when the refrigerant was low only had 150 grams left in the system at the time and was not really cooling. If yours stopped to do it when you recharged and now does it again are you sure it still charged? Does it still cools? Mine also does a cyclic humming noise continuously when ON. Not sure if it's the AC compressor or the tensioner pulley (I would assume there is more load on it when the compressor is running), I never investigated since it's barely audible.


New member
United Kingdom
BMW M328
When something like this happens, it is usually the faulty compressor, so no gas refill will make it work. But is it cooling? If it is still cooling, then I don't think it is a big problem. But as you said, you should take your car to the workshop to have it properly checked. Because I guess you're just like me, I can't find faults in my car, or even if I do, I can't say the real problem. Forget about car A/C, my apartment A/C wasn't cooling, and I couldn't identify that the only reason it wasn't cooling was that it needs washing. It was the reliable aircon technician near me that was telling me this.
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