Ive been through that with my accord. First check the fan relay in the fuse box. After that (and this is what fixed the problem in my car) change the auxilary fan switch. Once I replaced that, the fan never stayed on after I shut off the car. Keep an eye on your temp until you fix this. My car would try overheating everytime i was stuck in traffic. It causes the fan not to turn on when the car is running, but it will turn on when the car is shut off. Hint - If your temp stars going up, turn on your AC.