Hi. The cause of your problem is the heater rehostat. its mounted above the front passenger footwell. You may have had a burning smell before it actually failed. You can get them at a Ford dealer, and are fairly straight forward to fit. I beleive you get a small loom in the kit. You are looking for a 2 inch by 2.5 inch metal item, usually mounted in the ducting to keep it cool in the airstream. Good luck.
Paul
January 2008