Is it the original Fan blower motor for your truck? If so, it's probably time to replace it. I just replaced mine a couple weeks ago. It worked okay during the winter, though noticeably weak. Then when the warm weather came it wouldn't blow at all. When I got it out I could barely move the motor shaft with my hand. That thing was just worn, rusted, and crusted. Not bad, for a 23+ year old motor. Also, my fuse panel below the drivers side dash uses one fuse for both heat and a/c. Mine was labeled from the factory. Yours might be in the same spot as well.