C40-8W radiator component

On the rear of this C40-8W http://www.railpictures.net/viewphoto.php?id=149609 there is a a satellite television type dish that can be clearly seen through the wire screen. What does this satellite television type dish do?

That's the AC motor-driven radiator cooling fan...

Forgive me, but AC in "That's the AC motor-driven radiator cooling fan..." means Air Conditioner?

AC as in alternating current.

You are seeing the shroud, that holds the A/C motor driven cooling fan, for the engine radiators. The air compressor is also motor operated, instead of driveshaft driven, from the diesel. Regards

So even though a C40-8W is a Direct Current locomotive there is some alternating current componets in there?
Thank you for your responses so far.

These units send direct current only to the traction motors. The main alternator produces three phase AC which is "rectified" (changed to DC) for traction purposes using silicon diodes. Auxiliary components (such as the radiator fan, equipment blowers, and the air compressor) use AC.

Thanks for all your responses they have enlightened me.