807 fan/heater won't turn on - dial control -

[summertime]

Hi

Went to turn the fan/heater on to de-mist and warm up the car today, and although the dial turns it doesn't turn anything on at all. The dial is 'just' turning, the markers aren't changing to show how far it would be working either. I don't think it's the actual heater, just the dial?? This happened once before and after a short time it started spontaneously. Obviously we can't drive it at the moment because we can't see! never mind the chill factor ;-)

Any help would be brilliant!
Thank you :-)

Summer