Check the fan itself - this is not easy task as everythink is boxed in plastic. What i see the intake fan is after the hard drives cages - but i didnt instal any 3,5 HDDs yet, so its as open as HP design allow - and both FANs are running ... you can see and hear it and also feel hot air flow on outtake site
GPU - i didnt instal GPU yet - just CPUs and RAM sticks
