You can feel in there with something to see if it moves as the vacuum hose is
disconnected and connected. At idle it should lift to allow warm air through
(except if the system is already hot). Pull the hose off and suck on it -
should hear the flap clonk as it moves to the stop, or feel in there as before.
The end detaches too (on my Polo anyway).

--
Dave.
UK VW Type 3 & 4 Club
http://www.hallvw.clara.co.uk/
------
"Colin" wrote in message
...
The vacuum operated flap in the air intake was stuck down so cold air was
always drawn in. Used to 'screw' (self tapper through the casing) the
thing
in the up position for winter and screw it down for summer running. Crude
but effective :-)

Thanks. I'll have a look at that tomorrow.
Why would the fault correct itself after the engine had been turned off for
a few seconds and then restarted?
(BTW: Is there an easy way to see if the flap is stuck?)

Thanks, Colin