The two electrical cooling fans keep running after engine shut down.

I have a 2000 ML320 and the dual fans run even after the car cuts off. The temperature gauge is fine when the car cuts off but the fans will not go off unless I unplug the connection under the hood. Sometimes after unplugging them and leaving them unplugged for a while I can plug it back up and the fan will not come back on. Sometimes it will come back on and not go off and even run the battery down. I have had to jump it off twice now because the fans would not cut off. I need to know what to do. Just started doing this out of the blue.