Fans are triggered to come on when the engine temp sensor reaches a certain resistance. This resistance is related to engine temp and a search on the forum will bring up what resistance the sensor should have per temp for checking it. It usually falls into a range of 217* for fans on and 208* for fans to turn off. If that is normal, and wiring is good all over the only thing that will cause them to not come on is the ECM. The ECM provides a ground in the circuit to start the fans.I bought new relays since one of mine was bad. Fans still do not spin when i pull and replace the maxifuse. Fans do run when i jump them. Is the next step to test the ECM? where is that and what does it look like? If its not that do i replace the temp sensor? Why else would my fans not come on?