No hot air blows out from vents near feet

I have a Citroen Xsara X reg. When I turn the heater controller from
windscreen to blow heat down by my feet, virtually no heat comes out. In
cold weather, because of this problem, the interior of the car takes ages to
heat up. It sounds as though there's plenty of air being pushed around
behind the dashboard somewhere, but altering the control seems to make
little difference.
Anyone have any ideas?
Thanks, Chrissssss.........

 

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Have you turned off all the other vents, such as side window vents and
centre dashboard?

Cic.

 

Yes I have, but it makes little difference. It's as though something isn't
opening behind the dash somewhere.

Chrisssss........

 

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You might have a few dead leaves trapped down there - the lowest point of
the system. Can you get a vacuum cleaner close enough to try sucking out the
obstruction?

Cic.

 

Many thanks Cicero. I'll give it a go. Appreciated. Chrisssss.......