CPU Fan Revving

[cav58d]

Intel I7-6700 with stock fan.  CPU Cooler fan is revving, and the change in RPM is very noticeable.  Happening with computer idling or light web browsing.

CPU temp is fine, anywhere from 28-21.  Fan is idling around 1,250 RPM but his it's momentary revs in the 1,400-1,700 RPM range.  It doesn't sound or feel right.  Any thoughts?

[Bizman]

It sounds like the the temperature sensors work and adjust the RPM just as they should. There's probably something wrong with the actual cooling element.

I can think of two culprits. The most common one is dust in the cooler fins. If there's a thick blanket of dust between the airflow and the finned block, the system will increase RPM to get through. Canned air is the remedy, but don't let it spin your fan! Unplug the fan from the motherboard and prevent it from rotating wildly.

The other potential issue is that the cooler isn't firmly attached. Especially the spliced plastic prongs can be tricky to get right and tight through the assembly holes. Carefully try to rock the cooler at each corner. If there's any slack, you've found the culprit. Wisdom by experience here...

[cav58d]

Thanks Biz, I will give it a go.

Re: forced air.  Is it okay if I use my finger to physically block the fan from spooling up as the air blows through?

[Drano]

What Biz said and if you find you'll have to reset the fan do yourself a massive favor and get ya one of those hyper 212+ coolers. They're like around 30 bucks and do a great job for the price. It'll fit the 2600k socket (and many others).

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[donnieboy]

What is acceptable temp range? Mine seems to run more than it needs to, but hesitant to change settings without knowing how hot is too hot.

[Bizman]

CPU temp? It depends on the model, but as a rule of thumb I'd say some 60 centigrade might be considered as a threshold. They don't burn to death any more, they just slow down to almost a total stop if the cooling fails.

[cav58d]

I followed the steps Biz offered.  I also went into Bios and q fan optimization and it automatically made some changes.  Still having the annoying problem.  Temporary jumps of a couple hundred RPM and as soon as it spoils up, it spoils right back down to normal idle.

[cav58d]

Also, after 1 hour of playing AH the CPU temp is only 38.  So the fan is doing its job, the revving is just annoying.  Still doesn't seem right.

[Drano]

Well if you reset the fan it's a silly question but you did replace the thermal compound when you did that right? Had to ask not knowing your level of techiness. It's an important step.


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[Bizman]

Did you actually check if the cooler is loose?

Also, if you did, as Drano said replacing the thermal compound is important. You don't need much of it, half of the size of a rice grain is enough for a processor core the size of a fingernail. The function for it is to fill tiny scratches between the heatsink and the core.

[cav58d]

Didn't know I needed to reapply thermal compound if I was putting the same Fan back on within 60 seconds of taking it off?

[Bizman]

Well, IF it's a fairly new system you MIGHT be able to reuse what's left in the center. The burrs are dirty and thus out of question. However, if the heatsink has been loose, there might be some dust or at least some oxidization also in the center. So better wipe it all off and add a dab of new stuff.

[Drano]

Yeah the dumbest amount of dirt up under there can affect heat transfer and that can affect your sensors that manage the fan speed. Best to just start over. Google the proper process for applying thermal compound. It's not hard. Remember - - less is more. If you think you didn't use enough--you're probably OK. Too much is bad.

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[AKIron]

Is the Power Supply fan the only fan moving the air out of the box? Is it working properly? Might just be getting too warm inside the box. Maybe add a case fan if you don't have one. Make sure it spins the right way. Don't want it in opposition to the power supply fan.

[Bizman]

What AKIron said, and even worse: Is there actually any fan taking care of the airflow inside the case? Many modern cases have the PSU in the bottom, taking care only of its own cooling with an air intake of its own in the bottom. If that's the case, case fans are crucial. The very minimum is one large exhaust fan uppermost in the rear. Otherwise you'd be circulating the same air over and over and when the air inside the case gets warm enough, the fan will add RPM to keep the CPU cool enough. The case temperature should stay just a tad over room temp.