Why does the fan in my desktop tower run so high when monitors are disabled?

"A fan speeding up is intended to counteract your system heating up. So, either your system is actually heating up (maybe you are playing a graphics intensive game or something) or your system ""thinks"" it is heating up when you are in single monitor mode.

With respect to the fans immediately quieting down when you switch from 1 monitor mode to 3 monitor mode: it doesn't make sense to me that they are correlated unless the configuration change changes the fan policy in your system in some way.

Otherwise, I know of no reason for you fan speed to be affected by your monitor configuration."