G2S Pro Extruder fan not working

[sischka]

I have assembled and tested my G2S Pro, everything works fine with the exception of the Hotend fan is there a command I can send to test the fan functionality ?

[Mark]

You can use M106 S 100 to check it.
refer to the link here:
http://www.reprap.org/wiki/G-code#M106:_Fan_On