caravan air blown heating not blowing hot air?

i have a sterling eccles explorer caravan and the air blown heating will not blow hot air. it did work last year although when the fans start up it made a squealing noise. after turning it on and off a few times it would work. now when i turn the air blowers on i just get a squealing noise for ages and the air only blows out cool even when the dial is set to hot.

jo
August 2009