Does the K2 run passive at all?
Id imagine it would give some passive cooling but not a lot. Not got at least 1 spare fan to slap on it?
Yep, though i never used that feature. On my old board i used a pwm splitter cable, new board in sig has 2x 4 pin pwm headers. Did you try a single fan on the cpu header?
And is this happening with both the 140mm and the 120mm fan when tested separately?
Would it not be the motherboard rather than cooler that would determine fan speed?
It would appear that the fans do not start unless the CPU is under stress!
Would have been nice to know this in the manual!!!
Yes, but I'm sure you get my drift. They do not start unless the temps or stress gets high.