Air conditioning hissing

[carlosfandango]

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
Carl

 

[GTI's]

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?

 

[vwengineer]

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.

 

[carlosfandango]

Thanks for the replies... I think I'm going to get someone to look at it to check for leaks before I go spending ages fault finding/fixing

 

[vwengineer]

If it's still cooling, it's probably something else than a leak