heater fan not working?

Hi. My heater fans are not working on my mercedes sprinter 311 cdi its a 2002 model lwb. Ive been told it may be the bushers but havent a clue where to start looking.I am capable of mending myself with a little help. Does any one know of a fuse it might be and if so where to find it?All fuses under steering wheel are ok.Are there any in the engine bay i need to check?I would be greatful for any help no matter how small. Its getting very cold now and would like a warm van. Thanks alot..