Fan failure mystery

Hello all,

I upgraded an aging system yesterday: Core i5 750, 4GB Gskill mem, Gigabyte P55M-UD2 mobo, HIS Radeon 5770 GPU, Coolermaster Hyper212+ HSF.

Existing components include a SATA 0.5TB, Antec case + TruePower II 550 PSU, 120mm case fans, and optical drive.

The new build worked perfectly upon completion. Successful POST, low system and CPU temps, everything running smoothly. I installed Win7 and fired up a couple of games. Everything was stable and temps were solid after a few hours of gaming.

This morning, I stuck in one of my old PATA drives with WinXP and my copy of Adobe CS4 in order to deactivate the Adobe product on that drive (dumb). A fan alarm went off, but all fans were still running. I went into the BIOS, deactivated the SYS fan failure warning and restarted. All good, fans still running and temps low. However, the system seemed to hang when updating the IDE drive list during POST. I waited, started smelling something burning, and quickly hit the power. I decided to take out the PATA drive, plug in the SATA and revert everything to the way it was last night.

After reverting, I fired up the computer and noticed that the CPU fan was not running (explains the burning smell... hope that CPU is still OK). I checked connections, everything looked fine but the fan wouldn't start. It jerks a bit when I hit the power switch, but that's it. I tried switching the CPU fan to the SYS fan header and vice versa. Both fans started running for a few seconds, but then the CPU fan abruptly cut out and the case fan (plugged into the CPU fan header) started whirring at full bore. Note that I also tried unplugging my optical drive, system fans, and hard drive to determine if the fan is not receiving sufficient power, but this didn't help.

This tells me is that my CPU temp sensor is still working, that it's still sending appropriate signals through the CPU fan header, and that low power is most likely not an issue... so the fan attached to the CPU is most likely faulty?

Why did the SYS fan trigger an alarm even though the CPU fan seems to be the dud? Do I buy a new fan for the CPU cooler and hope it works? Or could this be a problem with the motherboard?

Thank you in advance for any ideas!

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  1. the case fan went mental because your cpu was frying and it told the mobo to increase the rpms on the cpu fan, which ofc was the case fan plugged into cpu header,
    I think your cpu fan is dead tbh, find another 3pin fan and see if that works ok in the cpu header that should rule out it being the mobo's fault, Ill check back when I can get to my pc at home :-)
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