I'd take a look at the fan itself, under the cowling. First test I'd do is a voltage check at the fan wires. ETM suggests switching on the ignition to Run, setting fan speed to high, and turning the A/C switch on. If you see 12VDC on the fan terminals, check the fan motor. If you don't see 12VDC, check the resistor pack for damage.
That resistor pack has an integrated overload breaker, I've seen them fail completely.
If the fan works only on high speed, it's also the resistor pack located inside the fan cage.
New packs aren't that expensive.If the fan doesn't work at all, or squealed a lot before it stopped, it could be seized bearings in the fan motor, or a warped fan cage.
I've never seen an HVAC switch fail, but that's a possibility as well.