Using D8 for extruder fan

Hi

My 3D printer is a Prusa i3 Hephestos without a heated bed.
This means that it has an unused D8 output. Now I want to connect the extruder/electronics fans to D8.
I already tried to change "fan pin for board cooling" to heater1 or digital pin 8 in the repetier configuration tool but that didn't work.
Do you know what else I could try?

Edit: the fans are running when using the blink sketch for pin 8. So it doesn't seem to be an electric issue

Edited 1 time(s). Last edit at 11/05/2015 03:43PM by MaxMKA.

Make sure no other part is using the pin. So especially make sure you have no bed compiled in or it will set it to 0 all the time.

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The bed is disabled and I have checked pins.h. Only HEATER_1_PIN is set to 8.
How do I find out which part of the firmware is resetting D8?
Attached is my configuration file.