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CPU fan running full speed all the time

Posted: Sun Aug 09, 2020 1:58 am
by Nuby1Canuby
My wife's old Q6600 PC Blue screened and after that you could hear a fan running obnoxiously loud all the time. I popped the side off and you could hear it was the CPU fan.

I tried disconnecting and reconnecting the 4 pin fan cable but that made no difference. It's a small mid tower case with a snorkel on the fan so finding a replacement would be difficult.
I tried plugging the fan cable into the 3 pin connection for the case fan since that wasn't running loudly. The CPU fan was still running full speed all the time.

I reset the BIOS by moving the jumper to clear the CMOS. (side note: the PC won't boot when the jumpers are on pins 2 and 3 or when you put it back on pin 1 only instead of 1 and 2 for normal)

The CPU fan is running normal speed again.
Of course I nudged the cable for the SSD while doing this so it wasn't showing up in the BIOS. Moved the SSD cable to a different SATA connector, which seems to be a tighter fit and all is well again.

Re: CPU fan running full speed all the time

Posted: Sun Aug 09, 2020 9:23 am
by FlyingPenguin
Sounds like something seriously glitched the CMOS memory. Did you check the CMOS battery? I've seen mobos act very strange when the voltage gets low.