1999 Ford Windstar

I had problems with the heat this winter. It just didn't produce any hot air. The blower worked O.K. But now this summer, the air-cond. Works fine but the fan in the dash only works on high. Although the rear fan works fine. Is it more likely that the switch is bad or the fan motor may be bad? Can it be easily checked without removing the switch from the dash? Also where is the fan motor located? I will be glad to make a donation. I would appreciate any assistance you may be able to give. Thanks, Paul