Well, first, is it a Ford Chassis, Chevy, or something else? Next, if you have no power to the fan motor, how do you know it is good?
Now for a little help. It should be a 30 amp fuse. Also has a speed control. Some even have a relay, for Ford, it is in the under hood fuse box. Try it on all speeds, if it works on high, then it is the speed control. If the fuse is good, and has power on it with the key on, then you are left with the switch, or the relay,
Ford manuals can be found here:
2012 Ford F250 ext. Cab 4x4
2002 Jeep Wrangler Sahara
2008 Yamaha V-Star 650 Classic
2008 Work and Play 18LT