looking at a 1996 Mazda 626 and the fans do not work and owner states fan fuse is melted. possible causes ?

I would check the wiring going to the fans, it could be a bad relay or a short. this would cause a fuse to melt but usually the fans are controlled with a relay so that the fans are not drawing direct current through the fuse block. it could be a temp sensor issue as well. i would break out a volt meter and wiring diagram and see if the fan circuit is on the fuse block with another circuit.

It might also simply be a bad radiator temp sensor. Usually a cheap and easy fix. If you check all of the above and can find nothing, find the sensor, unplug the harness to it and "temporarily" short the two connections together. If the fans are on all the time then, its the sensor.