Heater on hot

[Colin211]

On my C220 w202 the heater blows hot air from the side vents when on cold any ideas ?

 

[C220GJS]

Probably because you have no power to the duovalve, which controls the water flow to the heater.When this valve loses electrical power it defaults to fully open.
Check none of your fuses in the main fusebox under the bonnet have blown,(fuses 3 and 11 and 14 used in heater system).

 

[Colin211]

Fuses all ok !

 

[television]

As George says the duo valve, if not the fuses they do stick and jam in the hot position, there is a DIY on thís

 

[Colin211]

Thanks how can i sort this duo valve ?

 

[Andy Wr]

Search for duo valve maintenance by parrot of doom or easier still press this link. http://forums.mercedesclub.org.uk/showthread.php?t=25909

 

[Dirtyharry]

i get the same problem on my W203. if i turn the dial from cold to hot it doesn't always work the first time, but when you do it twice it works for me ?

 

[Colin211]

Thanks for all your help will take a look at it the weekend