Cooling Fan Problem

I have a 1999 Plymouth Neon that the cooling fans stopped working. The fans themselves work.
I had little time to diagnose the problem. I was able to hook the fans directly up to the battery and they worked. The fuse is also ok. For now I hooked the fan up to a toggle switch so I'm able to turn them on manually but I need to get it fixed.
What else is in the cooling fan system? I assume there's a relay somewhere and a couple sensors? Are there common problems that cause this?

There is both a relay (located on inner fender well drivers side) slide under and follow the wiring harness from the fan motor/s, and a temperature sensor, near thermostat housing on DOHC models.