2005 E270 CDi - heater blowing cold air only

[Marko47]

As above. Just as the weather takes a turn for the worst, the heater decides to only blow cold air. Everything else appears to be in order. Any suggestions?

thanks

 

[Larkone]

Get a reader and check the live values for the flap actuators - it will show if they moving or not as you change the heating controls

 

[Blobcat]

Duo-Valve most likely sticking

 

[Marko47]

Cheers.