My W212 has the same problem many do, which is a slight mildew smell when first turning on the AC occasionally. There's a fan noise I am familiar with, which is that of the LED lights that continue to cool them after the car is off. However the last few days I've noticed a humming/blower sound coming from near the passenger side firewall, which is where the HVAC has an intake and you can actually see the blower cage if you remove some plastic.

I'm assuming that this is intentional and is the blower running in an attempt to dry out the moisture, but I wanted to check in here to see if anyone knew for sure...?

 

This is kind of a nice feature. How long have you ovserved the blower run for ?

Do you think that can help push an old system battery over the edge??

 

I presume you guys know about these little minty marvels?

Lubegard 96030 Kool-It Evaporator and Heater Foam Cleaner

if not, copy/paste that into Amazon to see them.

I usually do mine once a year, maybe twice if needed by the end of summer. I just did the first one for the year a few weeks ago, and like usual, the puddle underneath was nasty. First time I did it, I had to do it 3 times before the puddle was clear, it was that nasty. First can puddle came out looking like coffee. Second can like chocolate milk, third can was clear. Now when I do it, it looks like lemonade with a bit of a beige hue. But sure does fix it.

I will also set the vents to upper cabin and put a little through the center stack vents. That makes a big difference too.

to answer the main question though - I’ve never noticed mine running the blower motor after the car was shut off. I have the led fan whine, but never the hvac blower motor..

 

no extra blower fan here either have engine off and I climb out and I run my AC about 75% of the year due to wear I live in deep south.

Funny thing is the LED Fan or whatever it is near headlights comes on all the time it seems.
Yesterday I had to check mileage for soem reason, car was sitting for 3 days since last driven so it was AMBIENT (70's in my garage) I open door and WHIRRRRRRRRRRRRRR the LED fan comes on.
WHY? I check mileage, shut door and fanstill running even as I walk back inside...

Cannot be good for battery IMO.

So how can LED lights be more efficient if MB has this dumb fan come on to cool them off?

SOrry for sidebar but he LED fan is annoying

 

My blower ever run too, when engine already OFF, but it does not turn ON immediately after engine kill.
Like 5-10 minutes later.

It is a very slow spin, almost whisper quiet, unless you open up the air box ( above the battery ).

Yes, that is to reduce water moisture from EVAP condensing.

 

That sounds like what I'm hearing, thank you.

 

replace your cabin filter with

Mahle Caremetix
Mann FreciousPlus
Hengst Biofunctional

All these kill off bacteria/mold and have superb construction and filtration properties better than the units these cars shipped with. The mann carbon filters for $20 or so are absolutely inferior to the MB branded Mann filter, and use different materials. Moisture accumulating in your vents is because there isn't enough airflow and there is a moisture buildup, so the filter gets clogged over time

Retain your slider clip from the old MB genuine filter if you have it, nothing on the market fits the same. Eventually the mildew dries out, dies and gets sucked into the filter

If you want to be thorough, I recommend this product highly

 

An unobstructed filter helps knock down the particles level but the filter sits on the INTAKE side of the AC evap coil .... from there the fresh mildew spores fly directly out from each vents.

The car interior surfaces are coated with these contaminants until circulated back through the HVAC intake HEPA filter.


Slopped parking:
When the car is parked on a slopped driveway, part of the condensate has no chance to discharge out ... it brews existing colonies of germs


Where there's a will there's a way:
let's think of a handy HVAC mod for cleaner air. (spray cleaning the coil is item No1)

You know the home HEPA filtration towers from Costco or big home stores... inside there is :

• a blower,
• a multi layer filter,
• a UV tube and
• a high-voltage ionisation surface to charge particles with statics.

I bet we can find 12Volt parts on Internet to retrofit a small UV LED light source plus the static ionizer within the HVAC track to disturb the contaminants life cycle.

waterproof UV

Once ionized with a static charge, the light spores will stick to surfaces instead of being airborne inside the car!