Heater control Duovalve only or a flap?

[Rorcus]

My heater wasn't working at all and after changing the Duovalve I can get nice hot air, but if I then switch it back to cold it stays hot for ages until the heater matrix is obviously cooled down after the duovale has shut.

So is the w210's Hot/Cold purely controlled by the Duo valve or should it also be switching a flap/redirecting air around the matrix rather than through it when switched back to cold. I'm hoping the latter as this might also explain why KFit charged the Aircon without pressure loss but couldn't get any cold air in (so at least I got a refund )

Any ideas what to check test next?

Ta..

 

[Juls]

Interestingly Rorcus mine's stuck on hot in the passenger seat, so I dismantled the duovalve to clean it, but it was absolutely sparkling as if it was new... I dismantled the cabin pollen filter and cleaned out the leaves but it looks in good nick as well... Any other suggestions from anyone what else to check??