"Hissing" sound from the air vents

[sjw]

Got this noise that's coming constantly from the air vents, sounds in particular like it's coming from those that blow up onto the windscreen. Noise doesn't change with engine revs, or, seemingly, with air conditioning strength. Both the engine and the blowers must be on to hear it. Any thoughts?

[sjw]

https://drive.google.com/file/d/1-aNzsSmotAO3M_KDPTzR0vx8H9JnWqLR/view?usp=sharing

[bgbazz]

I had a similar issue about a year ago and it was very annoying...after much searching and investigation, it turned out to be foreign material trapped in the air con ducting and further inspection, it appeared to be small chunks of the felt like stuff that was being shed from the control flaps (doors) on the main housing around the matrix...apparently this stuff is used to create an airtight seal when the flaps are closed so that the air is directed to the appropriate outlet as required. Much mucking about with the air nozzle and vacuum cleaner produced a satisfactory result...quite a lot of the felty stuff was removed, along with the annoying noise.

[sjw]

I had a similar issue about a year ago and it was very annoying...after much searching and investigation, it turned out to be foreign material trapped in the air con ducting and further inspection, it appeared to be small chunks of the felt like stuff that was being shed from the control flaps (doors) on the main housing around the matrix...apparently this stuff is used to create an airtight seal when the flaps are closed so that the air is directed to the appropriate outlet as required. Much mucking about with the air nozzle and vacuum cleaner produced a satisfactory result...quite a lot of the felty stuff was removed, along with the annoying noise.

Interesting, thank you. I have been feeling lately like my air con wasn't as cold as before, so I did the flap recalibration. It was around then that I noticed the noise (although it may have been there before and I was listening for it.

I do also think that some of my vents are stronger/colder than others. Do you mean you sorted it yourself?

[bgbazz]

Yes, I did manage to do it myself...quite a lot of phaffing about, but it worked. I removed the directional vent outlets on the dash and inserted the vacuum hose into the ducting as far as I could while the fan was running on the high setting and then selected every outlet position in turn a couple of times. Quite surprised to see how much crud came out. Maybe a bit of overkill, but I also cleaned out the fan housing and the fan blades. The whole job lasted all afternoon but seems to have worked.

[sjw]

Just as an update to this - it's not when the blowers are on, it's when the A/C is on (ie. the A/C button is illuminated). It's also not all the time, and sometimes it will completely go away for a few seconds, then come back.

[madstaff]

My guess is that your low on refrigerant either due to age or you have a leak.

[bgbazz]

Sorry I have no more suggestions for you...when I select either AC or heating on mine, the blowers come on automatically, usually on the lowest fan speed and I can adjust that speed as required.

Hope you get it sorted out.

[JB GTI]

Not the same car but my Polo developed a hissing sound shortly after start up and then maybe randomly during a journey if it was quiet enough to hear it over engine/road noise. Mine was low on air con gas. No leaks, just age related 5 yrs old. Regassed. Problem solved and icy cold air con again and no hissing.

[sjw]

Thanks all. Before I even heard this hissing noise, I suspected there is a leak as well. I only got the air con regassed last summer. Ho hum.