Sinjin

I took the S6 to see our resident Audi tech Aaron to help me find the proper part number for the electric fan that sits behind the radiator. The fan is loose, and continues to run and make horrid racket when the HVAC unit is on and you shut the car off. So we talked to the parts guy and he had two numbers 4D0-959-455L and R. So we took to the car to try to find the part number. With Aaron digging, we found yet another part # 4B3-949-455C. So my question is, what heck is the part number to order? The car is a 2002 S6 and any help would be great.