My car did the same thing. Checked heater/switch resistor and it was noticeably damaged. Ford #YS4Z-18591-AA for $7.70 including tax. As stated earlier, it is a bit annoying getting to the resistor - mine had a black base and was located above the fan in the upper right side passenger foot well, (basically behind the glove box).

Originally posted by LUCA:
Yep. You can be Phil too if you'd like.