How come the radiator fan won't stop running after you shut the car off?

When you say it won't stop running - do you mean that after the normal allotted time of 5-10 minutes it still continues to run? Many car fans will run about 5-10 minutes but not necessarily longer. Depending on the make/model of your vehicle - you may want to call the dealer for any "recalls" on your car if the fan doesn't shut off after 10 minutes.