1991 Chevy Beretta cooling fan

Having a cooling fan problem the fan wont turn on, so I replaced fan relay switch that did not work and I let the car run to normal operating temp to conclude all test's. Then when that did not work I hard wired the fan to battery and the fan motor worked, all fuse's have been checked and I narrowed it down to either the ecu or the temperature sending unit. I want to try replacing the sending unit and see if that works but I don't know where it is on my car so if someone could tell me where it's located that would be great thank you.