Okay so I have a 1998 540i and I washed the engine bay. After I washed the engine bay I started the car to warm up the bay and dry up all the water. It started normally and a few minutes later the auxillary fan came on and was running at full speed. It has been two days and it still runs at full speed from the moment you put the key in posion 2 until you turn the engine off. It has never done this before. How do I fix this?