Hi everyone!
Newbie here and in MB world in general. My W211 has about 230k km's on it and is has a pretty nasty smell coming out the vents no matter if heat or AC is on. I went to Canadian Tire and bought a can with supposedly cleaner that you turn on and close doors with full blast AC with air re circulation on. But I think that made it worse... I was looking at products like this, looks like it's basically a foam that expands within the heater core/evaporator and cleans out all the nastiness magically. Has anyone had experience with this or any other product that does the trick? Any how to's would be much appreciated as well
Thanks!

I'd start with changing the air filters. Depending on your model, there may be cabin filters below the glove compartment that you can change or it may be one single air filter under the hood in the rear left section of the bay.

The old filters could be musty and gross... but I'd start there before I started spraying foams into the vents.

^^^^^ X1

if it smells like burned rubber, look up one of my old posts

more insight as what is the issue??

OP, turn on the carbon air filter, that's the last button to the right on the ac control, it activates carbon filter and see if that helps.

Pretty sure his 09 doesn't have the option to "Activate" it as I've read the previous models can. But he can still get the carbon air filter and it just functions automatically.

Evap coils may need to soak in some klima detergent... also you must change the air filters

additionally if still bad you can run an ozone machine for 30 min in the car on recirc air mode

Thank you, sorry I should have mentioned that I changed the under the hood filter that was pretty much the first thing I tried But I've never heard of the glove department filters - is it possible for my model year to have both?

So you mean just replace the OEM filter with carbon type filters or would the carbon filters go somewhere else?
And yeah there is no Activate button anywhere around the HVAC controls...

on my car the rubber flaps inside the heater box were melting

Just came back from a quick drive, it's pretty clear it's not melting or rubber but rather a dusty/old kind of smell...

So ozone or foam, that's the question now

ozone won't leave a residue...

Does your car have the optional four-zone climate control, with the rear seat controls and vents on the B pillars? If so, you'll have a regular pollen filter under the hood and two charcoal filters under the dash.

If you have the standard dual-zone climate control, you'll have a combination pollen and charcoal filter under the hood and no provision for filters under the dash.

The underhood filters are the same size and physically interchangeable, but if you have the standard dual-zone climate control you need to make sure you get the "combination" filter in order to get the odor absorbing benefits of the charcoal.

An ozone generator would be the best way to deal with the odor as it leaves no residue and uses no chemicals, as long as the source of the odor isn't still present. Have you cleaned out the fresh air intake yet? If there's a lot of leaves and debris built up, it can cause a musty smell. Same thing for standing water anywhere in the system, make sure the evaporator drain is clear. Could even be a dead mouse somewhere.

If you don't have access to an ozone machine, most detail shops have one to deal with cars that have been smoked in. There's also the Dakota Odor Bomb if you wanted to try another product first. They make a neutral one that won't leave a lingering odor.