tapping/thumping noise

[merc_forever]

I have an 04 CLK that has recently developed a noise. It seems be directly behind the glove box and is like a tapping noise every second. It comes on with ignition before engine starts so not engine related and stays on after I take key out for a time. I think it is related to the heating? Is there a vent which tries to open/close when you put the key in the ignition? Maybe this is stuck?

 

[Dieselman]

Broken heater flap linkage.

 

[BlackC55]

as above. A long winded job to fix properly. 9/10 the dash has to come out as well as the heater box for repair.

 

[merc_forever]

Thanks! The heater still works and sound stops after a few minutes, what function does the heater flap have?