Car not telling fans to turn on

Hey.
i drive a 1999 toyota corolla, 2 wheel front wheel drive., It runs smooth. But until lastnight it overheated. All in all I found out the fans werent tunrin on any more.

i ran some ground wires from the battery to the fans and the fans work perfectly. Im guessing its maybe the sensors or the computer but I have no idea where to find the temperature sensor for the computer nor the computer, or mayb im jus wrog n those are not the problems if any one has an idea wuts up ill be very much obliged to get a reply.