1998 Buick Lesabre Heater Blower

Even though the engine has been warmed to 190 degrees at an idle (outside temp is below zero) the blower will not kick on, thus the inside of the car remains cold. After driving at road speeds for about 5 miles, blower will kick in and you get all of the heat you need. Battery is new and alternator is charging where it should be. It appears that something is telling the blower fan not to run like a sensor or something? Thanks