I've just had this, typical, the first day with a thick frosty windscreen to clear and the blower stops working on all settings.
Pulled the blower out (relatively easy job for a contortionist with a screwdriver!), tested the socket and it showed juice was present. Put the blower on the bench, put 12v across the terminals and it sprung to life! Loads of dust accumulated on it so blew it all off with compressed air, plugged it back in and it worked on all settings so screwed it back into place. Job's a good 'un.
but how very strange??