Determining how to make 7 wire DC motor run?
This is made by a large German company that specialises in fans, blowers, motors and some fuel-air burners for boilers and the like.

The Finnish web site has a model selection guide online. From this we can surmise the specifications.


R : no cowling, centrifugal, one sided inlet.
1 : 1 HALL sensor 
G : electronicly commutated
175 : blade diameter (mm I expect)
-AF : mechanical model
33 : electrical arrangement
-11 : mechanical arrangement


Lots of good manuals on the US site including a catalogue mentioning a model R1G 120 that has connection information on a missing page 259.  It seems to be a similar fan with DC operation and elsewhere a speed sensing output and a control input are mentioned.

As mentioned in a comment if the blue and red wires are connected in the fan they are likely the power wires at perhaps 12 to 48 V (model dependant) and the other two colours are the sense and control.

EDIT:
Page 180 of this catalogue shows a connection diagram with familiar wire colours.  Later in the catalogue there are a full series of diagrams starting on page 258 as predicted in the catalogue excerpt linked above.  All that remains is to figure out the appropriate type.  From the photo it is clear that the fan is 12V nominal.