Radiator Fan Troubles

I have a 97' Mustang with the 3.8l. Its been running HOT, I believe that I got a little a head of myself and installed a new fan motor. It still dosent work (only when the a/c is on) so now I believe that I should of checked my relay, and my coolant temp sensor first. The plug to the sensor has power the sensor does not. Can anyone tell me where to find this relay, and how to tell if it is bad? Thanks for any help.