Cls219 blowing cold air?

[DSK]

So the car was serviced last week and all seems well. On a motorway drive today, despite turning the temperature controls to high/hot, the centre air vents still blew cold but, hot air from the lower sections certainly warmed the cabin. It’s never been like this, the coolant was not touched and is bang on max.

The climate settings I’ve double checked and they are set as they always have been, since 2019. The engine temperature behaviour is also perfect.

I had another quick look and despite the garage changing a v belt, i can’t say they’ve caused it or, find anything obvious they could have disturbed.


Any ideas what could be causing this?


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[Rotorhead500]

Heat exchanger up the duff???

 

[DSK]

If you mean heater matrix would there not be coolant loss associated with that?


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[sonic]

I assume the used to blow hot air?
I am not absolutely certain but I don't think my E350CDI ever blows hot air out of the fresh air vents.

 

[DSK]

They used to as I’ve never noticed and issue/felt this discomfort despite it being the daily work horse for all.


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[mersum1es]

water changeover valve went bad, air duct flaps malfunctioning...

 

[Wighty]

I think it’s called the duo valve ? It’s a cheapish part (£50?) but a right fiddle to fit .
Plenty on YouTube .

 

[DSK]

Grazie Mille, I will get one of those valves ordered up and then get it booked in.


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