W211 Hardly Any Air Flow Through Dash Vents

[rgracin]

My air con has been working fine, until this morning when I noticed that there was little airflow through the dash vents. It didn't seem to make any difference when I changed the rotary controls to full face, or full windscreen/floor etc.

The fan speed changes, but hardly any difference in flow through the vents.

What little that was coming through was cold.

I'm assuming it's some kind of control module that moves some flaps in the system. Any ideas which one, and how to replace it?

Thanks

 

[Trickythemerc]

Could be a blend flap stepper motor problem, they tend to strip the plastic gears and are a bitch to get to. Depending on which ones have failed it can be a dash out job to fix them.

 

[rgracin]

If it was a stepper motor, could I expect there to be some change of flow to at least one of the settings? At the moment, nothing changes regardless of what setting, so if I go full screen, hardly anything comes out of the dash top screen vent.

 

[Ted]

Replace or clean the cabin filter before spending any dosh on it.
I've cleaned a couple of mine in soapy water - make sure it is fully dry before putting it back in or the flow will stay restricted for a good while.

You can check the airflow with the filter out.

 

[rgracin]

Update.

When I went back to the car last night, there was an usually large pool of clean water under it. I'm now thinking that the evaporator had iced up, and the water is from it defrosting. When I drove it last night, all was well again and air con was blowing icy cold.

So, some research tells me this can be caused by either low refrigerant, or a faulty sensor? Seemed to work well last night, so not sure on the gas front.

Anyone know what potential sensors i should be looking at?

 

[mmfkf]

Hi,
may still be worth checking the cabin/pollen filter as easy to check for blockage, paper filter.

when I bought my car changed the filter along with all the others and it must not have changed for some time and had plenty of debris in it.

 

[daveenty]

Had the same with mine (W212) on Sunday which, as you're all aware, was pretty warm.

Seems like similar symptoms, nothing through the centre vents irrespective of settings and a larger than normal "lake" under it when I parked it up. It's going into MB in the morning to be checked over as I've not used it since, but I'll let you know what they have to say about it.

 

[daveenty]

As an interim update, I just used the car briefly this morning and all is normal with the air con again. Cold as you like and all dash vents blowing to the maximum. It's due to be checked over at around 10 this morning so I'll see what MB have to say about it.