When each of mine (2) failed, they would do so intermittently. They'd be ok for a few minutes, then they'd start cycling on and off at the rate of ~1/2 to 4 times per second. The a/c clutch would cycle on and off at this rate which was not only annoying, but I'm sure would wear out the a/c clutch very fast. Notice large amounts of red dust around your a/c compressor clutch?
Remove the glove box (2 screws at the bottom of it). The thing has a 3 wire plug connector. Wires on my diagram (Haynes manual 89100) indicate red/black, brown/white, and green/red for 90-94 models in color; brown/yellow, green/white, yellow for 95-98 models.The far end of the thermoswitch is inside the evaporator so you're not likely to want to 'professionally' replace the thing. The switch is to keep the evap from icing. You might get another and insert the biz end of the thing into the evap coils as best you can.
I've also had Sooby relays fail when hot, too. There are several of these in the a/c system.
What I did, and perhaps what nobody else should do, as I may be toying with my safety:
Using a thermometer, my air hasn't ever been that cold (freezing) so I bypassed the thermoswitch. I forget which wires I hooked up to do this. From the diagram, I'm thinking that I hooked the (90-94 models) green/red to the brown/white.
Nick