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  cpu fan constantly running at max speed 
 
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Matt Muir Jan 31, 2008, 11:48am EST Reply - Quote - Report Abuse
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moved out of thread http://www.hardwareanalysis.com/content/topic/70469/ due to moving slightly off topic...

basically my cpu fan (Arctic freezer 64 pro) is running constantly at max speed despite having cool 'n' quiet enabled in bios. I've tried manually adjusting the speed using speedfan but this doesn't seem to work either. See my other messages for full details.

any ideas anyone?

thanks

M@


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john albrich Jan 31, 2008, 11:48pm EST Reply - Quote - Report Abuse
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Edited: Feb 01, 2008, 05:25am EST

 
>> Re: cpu fan constantly running at max speed
Try the swapping of the system and CPU fan method I described in the other thread to see if you detect a difference during POST. However...


Also, you may find out the CPU fan is in fact, NOT running at its maximum RPMS.

I have an 8VM series GigaByte motherboard, and it does the following normal things for that mobo:

1) BIOS says the CPU fan operates at ~2570-2600rpm
2) Does NOT vary/test the CPU fan speed during POST
3) Speedfan reports the speed accurately, but CANNOT change it

There is NO mechanism for controlling the fan speed in CMOS settings...it only reports the speed. It has a Fan failed "0rpm" detection option, which made it seem that the only reason it monitored the speed of the fan was to detect if it stopped spinning completely. The fan speed detected really must drop to 0 for the alarm to activate...a "fatally" slow fan will not activate this alarm.

While both BIOS/CMOS and Speedfan report the CPU fan speed is at a near constant ~2600rpm, it is NOT running at maximum speed during or after POST.

The CPU fan's maximum speed (achieved by supplying a straight un-modulated 12VDC to the fan) is approximately 3800rpm (determined by photo-tachometer)

So, like this GigaByte board, you may simply have a mobo that does not adjust the fan speed under normal conditions, and either keeps it running at a below-maximum value, and/or only speeds it up when the CPU temperature exceeds a much higher value*...which probably differs for each motherboard.


*edit to add--Being unable to get rid of the curiosity bug, I did a little more testing. I manually elevated the CPU temperature, and when it hit about 45C, the fan speed finally started to automatically increase. I got it to go up to ~3300rpm. On this system it is very difficult to get the CPU to heat up very much (a simple combination of low-CPU-speed and good heat-sink?) I had to add a hair dryer into the mix to raise the temp more than 5C. It normally runs within 5C of room temperature (at the base 2600rpm fan speed) no matter what program(s) I'm running.

Matt Muir Feb 01, 2008, 05:47am EST Reply - Quote - Report Abuse
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>> Re: cpu fan constantly running at max speed
Thanks for relaying the results of your experiments - you obviously have way too much time on your hands! To be honest I can't actually say I remember what speed the fan has been running at in the past but AC quote the fan being capable of speeds ranging from 900-200rpm - the main reason I suspect it's running faster is that my system seems much noisier than previously.

I do have a suspicion however that the fan is slightly rougher than previously so I might get in touch with the eBay seller (who appears to have a non-ebay computer shop too) and see if they actually deal with arctic cooling and can get spare fans.

Thanks again for your help.

M@

john albrich Feb 01, 2008, 08:38am EST Reply - Quote - Report Abuse
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>> Re: cpu fan constantly running at max speed
Matt Muir said:
Thanks for relaying the results of your experiments - you obviously have way too much time on your hands!...the main reason I suspect it's running faster is that my system seems much noisier than previously....


Actually, they only took about 20 minutes or so...not that much time.

Did you check that the heat-sink and fan fins are all clear of dirt/debris on all sides? That can also cause increased noise...although the noise build-up is usually so gradual over time one doesn't notice it.

Another reason it might run faster over time is that heat-sink pastes eventually degrade/dry-out, or the heat-sink has been mis-aligned...causing a less efficient transfer of heat from the CPU to the heat-sink. The fan has to run faster to compensate.

J B Feb 15, 2009, 03:29pm EST Reply - Quote - Report Abuse
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>> Re: cpu fan constantly running at max speed
OK The Fan might be too tightly bolted to the CPUI
I recently cleaned mine out and installed a sock as dust filter and suddenly the CPU fan stayed on constantly.
Previously to that the fan was pretty annoying...when using some progams.
When I took it off there was this graphite like substance in there between the fan and the CPU I cleaned it off.
To make a long story short...
The next day I remebered that "crimping"(too tight in spite of the spring loading) could be the cause...
I removed the fan again cleaned it more and then placed in several layers of aluminiun foil to dampen vibrations from the fan and transmit heat vibrations.
When I replace the heat sink part of the fan to the CPU I just turned the screws 1 full turn.
MY GUESS IS THAT MANY FACTORY FAN INSTALLS ARE TOO TIGHT
I the case of E machine T3516 this was the case all that time the fan heat sink was pressurizing the CPU enough to interfere with the smooth flow of electricty.
almost 100% of non-process related CPU/FAN(on) troubles can be traced to this problem.
THE FAN IS TOO TIGHT TO THE CPU
LOOSEN THE SCREWS
IF THAT DOESNT WORK RNR THE CPU THEN USE FOIL AS THE VIBRATION SUPRESSOR



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