If you're fan isn't coming on, it could be a faulty blower motor. This just happened to me last month.
The blower motor is located in the center of the firewall, right behind the engine. Check if you have power at the blower motor connection with the key turned forward and the fan turned on (DON'T DO THIS WITH THE ENGINE RUNNING - you have to lean over the belts). It's easiest to disconnect the connector to check. If you have power, it's likely a faulty blower motor. Reconnect the wiring & try tapping on the motor housing - sometimes this will start the motor if it's just on the verge of going (it will get you by in those emergency situations until you change the motor).
If you don't have power, it could be a faulty controller. Check the link I posted earlier in this thread. You may find more clues to troubleshooting your problem there.
If you need to change the motor, pick one up at your local autoparts store & get prepared for a job requiring a little patience & determination. Unplug the electrical connector and disconnect the motor end of the hose leading from the firewall to the motor. Unscrew the motor from the firewall. Now comes the part requiring determination. On some models (like mine) you cannot get the motor out of the engine compartment without removing the cross-member tying the strut towers together.
You should also remove the fuse & relay access cover at the back of the engine compartment on the firewall. Even after removing these, it takes twisting and maneuvering to get the motor out. And installing the new one takes even more patience as you don't want to force it the wrong way & damage it. BUT, believe me, it is possible.
NOTE: It is easier to install the hose to the motor BEFORE you maneuver it into position. Disconnect the hose from the firewall & install in the motor while you have it out of the engine compartment. Trust me - I tried to do it the other way and it was an exercise in frustration.
-C