heater blowers on blink!!!!! not good!!!

hi all, my blowers are not working in my 200tdi 90 defender at the mo, ive been told that it may be full of mud from and therefore failing the motor to spin?? i changed the fuse as it was was blown, and soon as i turned heaters on the fuse blew again?? could this still be to do with the mud scenareo?? if so can i clean the mud out???and diagrams or step by step guides to stripping the heater would be appricated. if not ive scanned ebay and found a few td5 heaters and 300 tdi heaters but no 200tdi, does this matter????????? any help is much appricated as im froze and i carnt see a bloody thing!!! haha

thanks

eddy