2005 X5 radiator fan

[TerryZ91]

Hi,
I have a 2005 x5 4.4 and I'm not sure if my radiator fan is working. Recently, I found coolant leaking from the expansion tank. So I looked at some stuff and noticed that the fan near the radiator does not come on at all. The car has maintained normal temperature and has never overheated. Probably due to cold winter air hitting the radiator. I left the car on and idling for 15 minutes and the fan never came on. The temperature gauge was in the middle. I did some research and found that some have two fan? (AUX and fan powered by the engine clutch)?? I have the 4.4 motor, i think N62. And I only have one fan, behind the radiator. There is nothing in front of the radiator. Also, the fan behind the radiator is not powered by the engine, it is not connected to the engine and looks like it is electrical. I took some picture so you can see what I'm talking about. My question is, is there any way to check to see if the fan is okay or do I just buy a new fan? Am I suppose to have two fans or is one fan normal for the model that I have?
Any help is appreciated. Thanks!