A quick way to test the circuit would be to disconnect the temperature sensor and the fan should come on. As a side note the fan should kick on when the thermistor resistance gets down to about 700 ohms.

I assume that by saying you "replaced the sensors" you included the coolant temp sensor? Make sure your grounds are good and check the quality of your coolant and associated hoses, electrolysis is a bear. While checking your cooling system make sure it is bled properly. An air pocket around your coolant temperature sensor will cause an improper reading.

Is your A/C working, if not, is it still attached? If you have removed it, you need to keep the button pushed in the "on" position or else the fan will not run. (on SOME shadows, it's just an odd thing about them) If that's not the case, please follow these steps:

Check the fuse and if applicable the fan relay (should be on the right fender)

Look for chinks, debris, etc in the harness(s)

Check your grounds. These cars are notorious for oil and other leaks, and enough bumps with that much lubricant will rattle a ground bolt free in short order.

If you have been overheating a lot the glycerol has probably done wonders for your electrical connections. Check them.

If nothing else works, hardwire the fan to an ignition switched circuit that is greater then 15A. The fan will simply run when the engine is on now. Always. You can also get creative and install a toggle switch for the fan inside the cabin run straight through the battery. I'd consider that a last resort though.

Best of luck!