Cusser
+1y
Easy: your blower resistor is bad. These are like 50 times more likely to go bad than the switch itself.
These are available new, like at AutoZone, for about $40. It has three resistor coils, and for highest speed there is no resistor, so it still works.
The blower fan motor itself only has two wires, so reduced voltage makes it turn slower, so your blower fan is OK.
Take out the glove box, maybe a dozen screws. There are two electrical connections to the blower resistor, which is held in by two screws to the top of the evaporator/air box, so you cannot see the coils until you disconnect the harnesses and take it out.
See