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I have been experiencing random crashes and other issues with my machine which lead me to ask questions about troubleshooting Prime95 failures. Unfortunately I Have not yet been able to resolve the issue. This evening in another attempt to do so I cracked my case to discover that my CPU fan was not spinning.

Based on BIOS screenshots I took at the time of my previous question I know that fan was working six months ago. It is important to note that at the time of the screenshots the CPU was at 61°C. Currently, according to SpeedFan all of my CPU cores are ranging between 34°C and 38°C. The CPU Fan Speed Control setting in the BIOS is set to Normal. Not sure if this setting is causing the motherboard to keep the fan off because it isn't needed at the CPU's current temperature (rendering my concern moot).

In an effort to troubleshoot the CPU fan problem I have disconnected the CPU fan and connected it to one of the motherboard case fan connections. When connected to the case fan pins the fan spins at full speed indicating that at least mechanically it is not to blame.

The pertinent machine specs:

A similar question Why does my CPU fan stop spinning after Windows Vista starts? has some potentially useful answers, but none of them go into much detail other than indicating this its probably "hardware problem." Should I be concerned that my CPU fan is not spinning? Is the CPU fan not spinning potentially the cause of my random resets?

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Speedfan is capable of completly stopping a PWM controlled fan, it is not likely but possible. Speedfan is not at all engaged when back in the bios though, many Motherboards have similar speed control software. In the Asus (I don't know gigabyte) software it is possible to have a cpu fan or a chassis fan (non PWM) completly stop, when cpu is cool enough.

It is possible for the 2 controls to be in conflict, With 2 softwares controlling the fans (speedfan and gigabyte softwares).

The "chassis" fans or other fan connectors are not usually PWM driven, although they can have 4 pins (weird), so there is a difference there. So in your hardware monitoring section of the bios, disable fan control (full speed) , and Disable speedfan from starting and re-test.

To disable speedfan from effecting things temporarily use Autoruns and disable it there and boot. Speedfan is not so easy to setup exactally right, it takes me hours to get it perfect (advanced fan control) and even after that a lot of live tweaking. If your having troubles, you should disable it right away , and test without it. Speedfan can work with other fan control software operating , but in this situation it would be a terrible thing to have on effecting your results.

Software for the hardware (gigabytes own controls) could also be disabled in both the bios, and its drivers in the OS (assuming you could find them) in autoruns (which can disable almost anything).

Right now with no fan going at all, you need to get back to nothing controlling it and it staying full speed always, then to go from there.

Depending on a lot of different factors it is possible even without high temperatures that the lack of properly operating fan could cause the system to fail. Intel has some really nice thermal safety and throttling, but even the application of "turbo" is boosting the speeds, and with that engaged, the sytem could indeed reset. Thermal safeties are there for emergency :-) not normal operations.

It is also possible to have a poor thermal connection to the heatsync, that allows the system to operate, but keeps burping the cpu to throttling or failing. Many people have fixed a odd cooling or throttling or failing situation with the CPU by just properly and more carefully remounting and checking the Heat sync the thermal compound, and its mounting sytem.

I will slightly disagree with your assesment that cold cpus do not need cooling, on the basis of they go from stand-by (C-states) to roaring at full speed in microseconds. So without some cooling or some place for the heat to go temporarily it should just shut down, in microseconds :-0

If it is before you get to the OS software operating of any sort, then you go direct to the bios. If it is after the OS loads , then "anything goes" at that point :-)

I would not be so quick to believe that the hardware itself is failing, when there are so many possible factors involved. One of the ways people will reduce software factors would be to boot into another system temporarily. "it works in linux" :-) Then it is some software in windows that needs adjusting.

other stuff: a 4pin fan is not nessisarily a PWM controlled fan, a PWM controlled fan can be nessisary on some boards CPU fan, usually it is known because it will complain that it didnt see it working. A non PWM controlled 4pin or 3pin fan can usually be made to work at full speed, depending on the design and the hookup of it, I have not bothered with that, just making sure i have a real 4pin real PWM fan for my CPU (at least).

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According to the specs of the fan that came with my heatsink I should have a PWM fan. That said I set the CPU Fan Speed Control to Disabled. At this setting the fan is now spinning at around 720RPM. I do not have Speedfan setup to auto run. I only reinstalled it to try and determine my CPU temperature when I discovered the fan issue this evening. Since the fan is now running (albeit at low speed its capable of 2000RPM) is the next step to remount the heatsink and apply fresh thermal paste? –  ahsteele Feb 5 '14 at 8:09
    
I would not re-do the heatsync until i could get the fan going full speed :-( I had the 212 thing and it was awesome with the 775 chips even pushing 2X the ammount of wattage, but when I went with a haswell chip , the 212 was a complete Dud (bad for that job). I dont know how that applies to the SandyBridge. Also other people were saying "Why do people like it" Well because it worked Great with the 775 chips. Tested both types too (evo and Plus). So i also have used the fan your using and get about 1800RPM out of them when on full? Does the MB manuel say anything about it? –  Psycogeek Feb 5 '14 at 9:30
    
I could not explain WHY the 212 was so bad with the new stuff, Crasy I pulled one right out of the working 775 computer, that could push 160Watts overclocked, and put it on the haswell doing about 100W and it could not keep it cool? Makes no sence at all, because the form factor the contact size, the pressure , are all very similar. –  Psycogeek Feb 5 '14 at 9:41
    
The fan is going 720rpm where? if you stop in the bios (and even read it via the bios) is it that low? and what are the fluxuations (as heard in your ears) when in the bios and then the OS? –  Psycogeek Feb 5 '14 at 9:46
    
sorry for my delayed reply I had a crazy week. In the BIOS and in Windows the fan spins at the same speed depending on processor temperature. There is no audible or monitored difference and it is definitely not spinning at its maximum speed. I have double checked that the CPU Fan Speed Control is Disabled. It seems that something else is preventing the CPU fan from spinning at maximum speed when connected to the CPU fan motherboard pins. –  ahsteele Feb 8 '14 at 4:35

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