HELP: How to adjust fan speed using coolbits in Xorg config file, Ubuntu system

I am a linux user. Currently I want to use coolbits to set the fan speed in my Titan Z card. However, my screen are attached to another GTX Titan Black card. when I want to set coolbits to 4 in the xorg.conf, it works fine for the card which is attached to a screen. However, if I did the same thing, it does not work for the card which is not connected to the screen.
Do you know how can I achieve this ? To adjust fan speed on a different card which is not connected to a screen

The following is some basic info:
Dell T7610 workstation:
Two Intel® Xeon® Processor E5-2620 v2
40GB ECC memory
Nvidia GTX Titan Z card
Nvidia GTX Titan Black card
The screens are attached to the Black card.
Driver version: 346.59
OS: Ubuntu 14.04