Clonking noise behind dash

[Ade1]

Car is a 2005 W203 c180 Kompressor Avantgarde. It has started making a noise, a rythmic thump thump every second. This goes on for a while, even with ignition off, stops then starts again when the ignition is turned on or when the engine is started. Whatever is making it seems to be located under the large de-misting vent.
Has anyone experienced this, or any idea what it could be ?

 

[Wighty]

Car is a 2005 W203 c180 Kompressor Avantgarde. It has started making a noise, a rythmic thump thump every second. This goes on for a while, even with ignition off, stops then starts again when the ignition is turned on or when the engine is started. Whatever is making it seems to be located under the large de-misting vent.
Has anyone experienced this, or any idea what it could be ?

Does it stop if you turn the fan and aircon off ?
Or when you close or open that vent ?

 

[Ade1]

I have not tried the aircon, as it has not worked for years now. I have operated the heater controls but it makes no difference.

 

[Ade1]

I may have answered my own question. Looking on YouTube there are several videos about faulty stepper motors that live behind the glove box, flapping away and making a similar noise. I will see about getting the glove box out to have a look, when it stops raining.