I have a 99 F150 XLT SC and I noticed about a month ago that the 2nd setting on the HVAC fan speed controll was out. There was no increase in fan speed when switched from Low to the 2nd setting. Now this weekend I was driving with the Fan set on the 3rd setting and I started to smell burning wire insulation. I thought it was coming from outside at first, but it did not clear after a few minutes. I was out of town for the rest of the weekend and I couldn't investigate it further. This morning coming into work it happened again, a burning smell when the fan is on the 3rd setting. There is no smell when it is on Low or when on Hi, just on the third setting. Anyone here have any ideas? Is the fan controlled at the switch in the cab or are the resistors on the motor? I'm just looking for some direction before I tear into this.
Thanks.

jj