B Class Aircon makes a hissy whispy sound through air vents and loss of cold air

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Active Member
Feb 10, 2016
Merc B Class W245
I've had my a/c re-gassed 3 times now in the last 12 months, my local independent garage did it twice (April 2016 and September 2016) and the most recent was 35 days ago at Kwik Fit - none of them could find a leak and now it has lost it's cold air again :(

I do hear a strange hissing/fizzing/whispery sound through the airvents when the a/c is switch on and this stops when I switch the a/c off and just have the fan blower on.

It almost sounds like the gas is escaping before my eyes!

I do hear the A/C pump switching on and off eachtime I activate it from the dash so I presume it's working there, but it just keeps losing cold air, any ideas guys?
Take it to an air-con specialist and get a Nitrogen pressure test done.

It'll be cheaper than keeping regassing it and better for the planet! :D
I recon you have a leak somewhere. Had a similar problem with mine a year or so ago and it needed a new condenser radiator. They are not located in the best place on a B class and get hit by stones and debris from the road. Had mine regassed over 18months ago and it;s still working fine. Probably what you are experiencing is the pump activates, realises there is little or no gas and shuts down.
Yes, the AC condensers area weak spot of both the A-class and B-class, usually hard to locate the leak using nitrogen pressure test or even UV leak detection dye, as they tend to go porous by corrosion on the rear side of the condenser facing the coolant radiator.
Best to find a proper AC specialist near you to confirm/repair rather than getting it re-gassed again.
The noise you hear is the refrigerant being sucked through the expansion valve rather than pushed, due to the low pressure.
OK I'll locate a mobile A/C specialist as this seems to be the next logical step.
In the mean time I just took it back to Kwik Fit who kindly regassed it free of charge as it only lasted the 45 days from last time, again they found no leak... wonder if I could keep bringing it back for free regassing!
Just kidding, like I have time for that!
Thanks for the inputs.

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