Heater fan won't turn on - 2001 Taurus

This just started happening when the weather turned very cold. I can manually operate the vent doors in all switch positions (and hear them move) but the fan motor will not turn on when that switch is moved to all positions. After quite a while, the fan will switch on. What would you tell a mechanic to check? Is this something better left to a Ford dealership to work on?

Thanks,
Charlie
charlie6067

Possible problems:
Fan motor is binding up. (bad bearings)
Faulty power supply to the fan.