Howling gale noise A207 E350 2012

[Barreti]

I collected my E350 yesterday and assumed the howling gale whistling noise from the heaters was because a vent was closed or partially open.
But I've opened all the vents and the noise is still there.
I think I've traced it to the passenger footwell but there is nothing obvious and I've poked my fingers into the square vent holes down there and can't feel anything, though you can't really get your fingers in very far.

Has anyone else had this and fixed it?

It sounds like sitting indoors when there is a howling gale outside.

Edited by Barreti on Monday 13th November 10:56

[Barreti]

Is it the cabin air filter?

I found this vid all about replacing the cabin air filter so I'll pull that out ad check everything is attached as it should be
https://www.youtube.com/watch?v=dWmODSQozyg

[Barreti]

Well it turns out the cabin air filter was the problem.
The H shaped white bracket which holds the filter in place was only picking up on 2 of the 4 tabs it slides over to lock the filter in place. Because of this it was allowing the system to pull air past one end of the filter and whistle/howl.
I'm not surprised really because getting the H shaped clamp to fit was a sod of a job -
well, in the car park in my suit it was. But its done now and quiet as a church in the cabin. Lovely!