Question Help! Messed with CPU cooler, now PC won't turn on.


Aug 10, 2015
I have a Corsair H100i liquid CPU cooler and have been tweaking the fan configurations for the CPU cooler and case. The H100i connects to the motherboard via a direct USB connection and one 3-pin fan header connection. It also has two fan connections which allow it to directly control the radiator fans. I have had the radiator fans connected through the H100i, but I didn't like the fan control as it only changes the fan speed based on the "H100i Temperature" which varies very little. I wanted the fans to modulate based on CPU temperature instead. So instead of having the radiator fans plugged into the H100i, I plugged them directly into the motherboard CPU_FAN header and then plugged the H100i 3-pin fan/pump connection in the CPU_OPT header. This worked nicely actually - I could leave the pump on full speed (which was fine as the noise level doesn't change noticeably at low or high speed for the pump - the fans are the noisy part) and could control the radiator fans through the BIOS and have them modulate based on CPU temperature.

Then I thought I would try swapping the fans to the CPU_OPT header and the pump to the CPU_FAN header to see if that would allow me to take the fans down to zero on the theory that with the pump running and the CPU at idle, just the natural convective cooling from the radiator would be adequate (it seemed that the CPU_FAN header would not allow zero fan speed). I did this and the computer started to boot and then shut down. Now it won't power on at all. The PSU seems to be fine (did a paperclip test).

One odd thing I noticed now is that the power LEDs on the graphics card which normally are on solid when the PSU is powered on (even if the PC is off) are now just doing a slow blinking. If I disconnect the power connections from the graphics card, then those LEDs turn red (which is normal). So it seems like some power is getting from the PSU to the graphics card. I took out the CPU to make sure it wasn't damaged and it looks totally fine.

Any ideas?

Here is my setup:

MB: Gigabyte GA-X99-SLI
CPU: Intel i7-5820K (running OC'd at 4.3 GHz)
RAM: G.SKILL Ripjaws 4 Series 32GB (4 x 8GB) 288-Pin DDR4
PSU: EVGA 220-G2-0750 (750W)
Corsair Hydro Series H100i GTX High Performance Liquid CPU Cooler CW-9060021-WW