Ahhhhh,

That's what I thought. Try changing your temp sensor. That's what tells the computer how hot the car is and when to turn the fan on and off. It also tells the car when it's warm and when the computer should switch from open loop to closed loop and vise-versa. If it's not working properly, your gas mileage will go to hell and your fan won't come on. I believe it's located in the thermostat housing if I remember correctly.

Good luck.

PS, it won't hurt to check the fuses either.