View Full Version : What could cause a CPU fan to blow loud after motherboard change?

03-27-2008, 08:05 PM
Does anybody know what could cause a CPU fan to blow very noisily after a motherboard change?

I just did a job for a client with a failed Micro-Star MS-661FM-L socket 478 motherboard. I replaced it with a Foxconn 661MX, which I believed to be of a very similar spec. The CPU is a Celeron D, a 2.8GHz IIRC.

The CPU fan, which was barely audible before, now sounds like it's blowing at full power. Checking the BIOS health monitor shows it's doing about 5000RPM and the CPU is at about 45 degrees C.

I remember the heatsink being a tight squeeze into the new motherboard socket, even though the sockets looked identical. I'm wondering now if it's not contacting the CPU properly, causing the fan to blow harder?

Also, I've had a look around in the BIOS for any noise reduction features. The only one I see mentioned is the option to run at 'Max Power Saving', but selecting this makes no difference.

There is nothing touching the fan that shouldn't, and it doesn't sound like it's failing or anything, just blowing very loud.

I'm concerned now that the old motherboard might have had some kind of noise reduction feature not present on the new board?

Any other ideas before I head back to tackle this one?

03-27-2008, 11:41 PM
The fan settings are usually in the "PC Health" section of the BIOS where the temperature is reported. It's been ages since I saw a new motherboard that doesn't have any kind of fan control! 45 degrees suggests that the heatsink is making enough contact. It wouldn't hurt to reseat it though.

Perhaps you could control the fan speed from within windows using Speedfan? But it's a bit of a bodge!

03-27-2008, 11:41 PM
It's possible the old motherboard controlled the fan speed, and now the new one doesn't.

Did you clean off the old thermal grease and apply a new batch?

03-28-2008, 07:52 AM
There definately isn't an option to control fan speed in the "PC Health" settings. It's all greyed out.

And yes, I did remove old thermal grease and apply fresh batch.

03-28-2008, 09:08 AM
If the BIOS doesn't have an option to control fan speed it must not, but I find it odd a new mobo doesn't have that. Is it possible you accidentally overclocked the processor, or maybe it was underclocked before.

Bryce W
03-28-2008, 09:16 AM
Either the CPU overheating due to it not contacting properly, insufficient thermal paste, or what Jory said with the bios fan control.

03-28-2008, 10:05 PM
I went back to the client today and took another look.

The CPU and heatsink were contacting just fine. Carefully cleaned and re-applied the thermal paste, but no difference.

I dug deeper and it turns out this particular motherboard does not have any form of fan speed control and just blows them at max continuosly.

I've looked for a replacement motherboard with automatic fan speed control, but it would appear the socket 478 variants are no longer made with this feature. I couldn't even find one on eBay.

Looks like I'm going to have to replace the CPU fan with something less powerful, and maybe disconnect the case fan completely.

03-28-2008, 10:45 PM
There is always normally a fan speed control. See if there are any bios updates which contain this feature.

03-28-2008, 10:52 PM
what about a fan controller?

03-29-2008, 03:59 AM
I would highly recommend not disconnecting any fan completely. They are there for a major reason. I find it really really odd that there is no motherboard out there not supporting fan control. I mean that is like a major feature for all systems laptop or desktop. If you cant find any motherboard to do this then I would suggest looking for a "quite" fan. Try to find one made of good quality that is just quite by design.

I would even try custom fitting a quite fan if none fits right before disconnecting it completely.

Or even do a custom fan control yourself. Should not be to hard. It does not take much power. for these fans and that is what controls the speed. How much power the bios lets goto the fan. Just rig up a custom power source and even a control knob with even lcd temp display for it etc.

03-29-2008, 09:28 AM
I find it really odd too that there is no fan control feature, but socket 478 is getting a bit long in the tooth and there is not much for sale out there for it anymore.

I've updated to the latest BIOS release which has made zero difference.

The fan controller suggestion is a good one, so I've ordered some of these: http://cgi.ebay.co.uk/FANMATE-2-Fan-Speed-Controller-Zalman-For-CPU-Case-Fan_W0QQitemZ150212773564QQihZ005QQcategoryZ3673QQ rdZ1QQssPageNameZWD1VQQ_trksidZp1638.m118.l1247QQc mdZViewItem

03-29-2008, 04:15 PM
Is it possible that the BIOS isn't detecting the fan and that's why it's "greyed out"? I don't mess with that type of thing much so I don't know. Is there a sensor wire of some sort on it?

03-29-2008, 06:13 PM
Is it possible that the BIOS isn't detecting the fan and that's why it's "greyed out"? I don't mess with that type of thing much so I don't know. Is there a sensor wire of some sort on it?

Well both CPU and case fan RPM speeds are being picked up in the BIOS, there is just no way to control them. Apparently that's the way Foxconn made these boards and their advice is to "get a better fan".

03-29-2008, 07:19 PM
I had no idea there was such a thing as a "fan controller". Let me know how they work out.

03-29-2008, 08:48 PM
fan controllers basically increase or decrease the amount of power going to the fan resulting in the fan speeding up or slowing down. You can get very simple ones that are no more than a little black box with a small knob or as fancy as an actual 5 1/2" bay drive enclosure that has multiple knobs for various fans and leds to make it glow.

03-29-2008, 09:59 PM
my guess is the voltage is higher