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Fan RPM and temp fluctuations

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  • Cases
  • CPUs
  • Fan Speed
Last response: in CPUs
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April 5, 2014 5:46:23 PM

CPU: 3770K (not OC'd)
Cooler: CM Hyper 212+

I dusted my case the other day and since then have noticed my CPU fan is fluctuating a lot. It'll jump hundreds of RPMs real quick for no reason. It's just idling and that happens. I also notice the temps have gotten a bit higher than usual, which explains the RPM jumps. When I first built my rig almost 2 years ago, temps sat around 20-30 C while idle. They are still in that range but usually sit more in the 30-35C range, but every now and then the temps jump to about 45C for a moment and drop back down.

My case needed a dusting but it wasn't anything too bad. I used canned air, always held it upright, used quick bursts and held the fan blades still. I didn't move the heatsink on the 212+. The only thing I can think of is that I blew a chunk of dust into the fan bearing or maybe even onto the CPU itself (where it meets the heatsink?). Like I said, it hasn't even been 2 years and I put the thermal grease on correctly. Tested it with Prime95 for about 12 minutes and the temps under full load are maybe 1-2 degrees higher than when I got it- nothing alarming.

Other than this, I've been monitoring my CPU load and it sits at about 14% with a few chrome tabs open. I don't notice any suspicious jumps in CPU load, but perhaps I have a malware issue?

Sorry for the long post, just trying to provide details.

More about : fan rpm temp fluctuations

a c 94 à CPUs
April 5, 2014 5:52:28 PM

recheck your cooler it could be loose on is base or have rotate a bit and do not made full contact so board send signal to cool the cpu and fan speed up it would be a good thing to repaste it .
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April 5, 2014 5:56:02 PM

I'm pretty OCD about the cooler so I want to leave it as a last resort. I also think I need to buy more thermal grease.

It'd be weird if it's loose though since I literally have not touched heatsink since I pasted it on 2 years ago.
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a c 142 à CPUs
April 5, 2014 5:58:21 PM

Depending on how sensitive your board is, the fan may jump with even a slight cpu load and temperature increase. The cpu clocking up from idle may be just enough.

Please make sure your board is controlling the fan by PWM if you can because some boards just too fast when using voltage based control(my media center board jumps like that so I use a slower fan so I do not hear it do it.).

As an example on one system

dead Idle
19-20c socket
32 core0

start some music(winamp)
24-25c socket
32 core0

Fan jumps from 690rpm to 760(it does it rather fast actually)

This only happens on this one system(others see no socket change). The socket(LGA technically) is calibrated by the board maker and the system seems to have a very low idle state because it takes about 10 watts less when idle vs playing music(while all my other systems take nothing extra to play music.).
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a c 94 à CPUs
April 5, 2014 5:58:26 PM

just check it in case .
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April 5, 2014 6:01:59 PM

@nukemaster

Now that I think about it, my board IS doing it by voltage. I thought it was PWM but it isn't.

Any reason voltages might be jumping more now than 2 years ago? My PSU is totally stable. Dust on the board or something?

@scout_03

is there any way to "check" without removing it and re-applying paste? Like I said, I need to get paste and would rather avoid scraping and re-applying since my original application was perfect. I have legit OCD so things like that are a huge huge ordeal for me.
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a c 94 à CPUs
April 5, 2014 6:06:12 PM

just recheck the screw on the cooler if they are tight and i would unplug and replug in the fan .
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April 5, 2014 6:08:21 PM

OK, will do all of these things, PWM switch, screws, fan. Didn't think of unplugging and replugging fan.

Still trying to figure out why the sudden change after dusting though. Could misplaced dust be a feasible problem? Perhaps I should re-dust as well.
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a c 94 à CPUs
April 5, 2014 6:10:02 PM

could be dust under the fan center unclip it from the cooler and check .
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April 5, 2014 6:11:39 PM

"could be dust under the fan center ."

I was thinking this was the case. There was quite a bit of dust lodged in the heatsink fins and I blew it all out. Perhaps a chunk of that floated where I can't see it.

Is it safe to blow canned air close to the actual CPU/thermal grease as well? Perhaps a chunk bounced into the space and is actually sitting at the base of the heatsink
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a c 94 à CPUs
April 5, 2014 6:16:24 PM

the dust wont go between the cooler and the cpu it wil go on the bottom of the cooler fin or on the motherboard could also stay stuck under the fan blades .
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April 5, 2014 6:19:04 PM

OK, thanks guys. I'll detach the CPU fan and give everything a good dusting again. I'll also re-tighten those screws. I'll get back in a day or two with what it was.

Thanks again to both of you.
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a c 94 à CPUs
April 5, 2014 6:21:42 PM

your welcome i be around .
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Best solution

a c 142 à CPUs
April 5, 2014 7:48:25 PM

I do not think it should jump more. but with aftermarket coolers being able to cool so fast(more area), it may be more of a fast drop than a quick rise.

When your cpu gets loaded(even for a short time) it gets a near instant spike in temperature. The board may just be over reacting. The board maker tends to set the amount of rise before reacting. Some boards may way for 5 degrees while others may react with every degree.

If you run the task manager you should be seeing these slight spikes in use even when loading websites and stuff.

I have had coolers mounted for years without any issues. While thermal paste may loose some performance it is not normally an issue as long as you do not move the cooler(since it kind of dries moving the cooler may cause further loss).

As long as the temps are in spec, I would just keep an eye on it and not loose any sleep over it.
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