WHats the most common reason why my fan doesn't turn on at the 3/4 line in my 94 Saturn with 160,000?

Check and test the fuse that powers the fan, coolant temperature sensor, fan relay if all okay to include the wiring -have the computer checked

Just to add to this one we went over this with you already. But we will go over this again unplug the bottom coolant temp sensor the one with two wires to it a black wire and yellow wire. Then start up the car is the radiator fan on?If so replace the bottom coolant temp sensor which is the coolant temp sensor for the computer. Also inspect the connector terminals to the sensor if there blue or green instead of silver you will have to replace the connector also. Let me know what you find.