Most of the time it will be a bad fan motor that has popped the fuse, or the relay is overloaded and failed. Here is a guide to help you test the fan motor, but I would check the fuses as well. Also, I have included a wiring diagram for the system so you can see how it works.
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.