CPU Fan Speed won't go above 975 RPM

I recently installed an Athlon II X4 640 - 3.0 Ghz AM3 CPU into an M4N78 SE mobo, and I've been having overheating issues when playing CPU intensive games.

At first I thought I applied the thermal paste bad, so I took it out and spent a long time cleaning CPU and heatsink to a shine.

Then I followed online guides and put the thermal paste on using the pea method rather than spread. This method is supposed to stop air bubbles forming.

This did lower average temps by a few degrees, but it still overheated when playing games.

Then I noticed my fans speed would never go much above 975.

I have SpeedFan installed for monitoring temps and fan speeds. I have Cool'n'Quiet enabled in the bios. Cool'n'Quiet definitely did lower temps and bring the crash rate down.

I went through the whole process of enabling automatic fan speed control based on temps, following an online guide, but the RPM still stays around 975.

I then went into the BIOS and enabled Smart Q-Fan and set it to put fan at 100% when temps reach 51c. But still no change in fan speed.

All my fans do seem to rev up at boot up though, so I don't think they are broken.

But it does seem the fact the CPU fan won;t speed up in accordance with the temp is causing the overheating.

Any ideas??

I have been thinking maybe uninstalling SpeedFan?
4 answers Last reply
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  1. replace the fan, it could be bad. wire the fan directly to a molex connector instead of the MB. if it runs faster while plugged into a molex then its not a fan issue but a MB issue.
  2. I don't have a cpu fan to molex adapter, so I just put in another fan I had from my last CPU to test and see if it was the fan at fault.

    This other fan is having the same problem. Just won't speed up to cool the cpu down. Q-Fan does absolutely nothing.

    Could this be something to do with the new CPU needing more voltage? Can I set this in the jumperfree configuration in the bios? It has settings for CPU voltage, but I'm inexperienced with CPU's/voltages and afraid to change anything without proper advice.

    Any help?
  3. Finally solved this!

    After much troubleshooting and frustration, I had the whole computer set up and running outside of the case and the CPU fan was running at 3500RPM average and CPU temp dropped right to 30c.

    I then tested it playing a CPU intensive game (FIFA 12) and the CPU only went to 38c and the CPU fan RPM went up to keep it cool! It was usually going up to around 70c before with the 975RPM.

    So that lead me to believe it was something in the case interfering with the fans voltage from the four pin power on the mobo.

    So, I put the whole thing back in it's case in same set up as I had just had it working and low and behold the fans RPM was back down and the CPU was running hot.

    Figuring the only thing that was different from outside the case to inside the case was the fact there is screws now touching the mobo, I decided to take them out one by one, booting up each time with one less screw, to see if was them. Starting logically with the screw closest to the cpu fans power pins, I hit the jackpot. It was that little bar steward causing some kind of voltage problem. I have it running now inside the case at a cool 32c and fan speed of 3169RPM.

    Also, the fact I removed the CPU a couple of times and completely messed up the thermal paste is encouraging to still have a cool CPU. So hopefully when I re-do the thermal paste properly it will be even cooler.

    I can now play some games! Thank jebus!
  4. very nice detective work. i commend you. :) glad its all working!
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