For those of you who got the model 4112N Papst Fans with the third wire, it is a temperature sensor. Here is a helpful link:
http://www.papstplc.com/features/articles/art012
What i'm really writing this post for is to ask if anyone has tried incorporating this sensor into their robot controller. I know it's not crucial and the fan does not draw too much power, but our team was going to play with it and see if we can get it to work. So anyone have any experience?