405 Heater

[delboy]

Hi Folks
I was hoping someone could help me please.
I can only manage to get cold air from the lower vents on my 405.
When I say lower I mean one ones up the side of the seats and foot wells.
The systems basic no aircon and the control dial for air distribution feels kind of ok and not like nothings conected.
Did I hear somewhere theres a flap that allows cold air in from outside that can stick open or was I dreaming??
Many thanks