2009 Clio heater stops working when switch put to mark 4?

Hi, When I put the car heater to mark 4 itblower stops working on my 2009 Renault Clio. The blower works on all the other settings. I did get a smell of burning yesterday but only for a short while & don't know if this is related to the same problem. Can someone help please?

Stephen
December 2015