Youre bouncing between a node on the fan curve. Ie. your fan curve says that below 70c fan speed is 25%, and above 70c fan speed is 50%. Your PC is going to 71c, then 69c, then 71c etc. You should be able to change the fan profile in BIOS. Answer from Deleted User on reddit.com
Tom's Hardware Forum
forums.tomshardware.com › home › components
One of my pc's fan's(or cpu or gpu fan) keeps increasing and decreasing speeds | Tom's Hardware Forum
July 16, 2017 - Choose to have it run under Manual, not Standard. Then set the specific speed you want. Make sure it is so high that it will never allow your CPU to overheat. When finished, SAVE and EXUT. 2. Instead, at that same place, create a custom fan response curve. What I suspect is happening is that your system often is running just on the border temperature between two fan speeds.
Reddit
reddit.com › r/buildapc › my computer has recently started increasing and decreasing fan speed repeatedly, almost like a siren. why?
r/buildapc on Reddit: My computer has recently started increasing and decreasing fan speed repeatedly, almost like a siren. Why?
May 22, 2021 -
Even when idle and not in a game or program that requires performance from CPU or GPU, the fans get pretty loud sometimes. And sometimes it has that thing which it is doing right now: Fans get LOOOOOOOOUD silent..... LOOOOOOOOUD silent....... LOOOOOOOOOOUD silent..... and it keeps going and is somehow really annoying. Why is that so? How can I fix it?
Edit: The intervall is like 5-7 seconds, so in that time it gets loud, stays for a second or two, then gets silent, and repeats on and on just like that.
Top answer 1 of 5
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Youre bouncing between a node on the fan curve. Ie. your fan curve says that below 70c fan speed is 25%, and above 70c fan speed is 50%. Your PC is going to 71c, then 69c, then 71c etc. You should be able to change the fan profile in BIOS.
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First I would ask what kind of motherboard you have because depending on the model your BIOS might allow you to have custom fan profiles. It is very possible that your temps are at the cusp of where they switch between being high rpm and low rpm. Also it depends on your fans, if you have PWM fans they should transition instead of switch between modes, usually fans like the Noctua Redux only have three fan modes, low / med / high so that might be something to look at as well. However I would recommend looking for fan settings first. Most motherboards that have this option allow some basic manipulation through the BIOS, but with more detailed tweaking using applications for example ASUS motherboards have AI Suite.
Videos
Asus
rog-forum.asus.com › t5 › hardware-build-advice › cpu-fan-won-t-slow-down-but-does-speed-up › td-p › 715785
CPU fan won't slow down but does speed up - Republic of Gamers Forum - 715785
March 7, 2024 - Thought resolved but doing it again. When using the PC normally the fan speeds increase and decrease as expected with load and temps. However, if I go into a game (in this instance, Rise of the Tomb Raider) the CPU fan heads up to full speed.
Tom's Hardware Forum
forums.tomshardware.com › home › cpus
CPU fan sudden/momentary increase then decrease. | Tom's Hardware Forum
December 6, 2010 - Just wondering if this is normal behaviour? The processor is an i5 760, the computer was idle (40C processor) when it happened. Thanks for any suggestions! ... Intel has Speedstep technology that automatically increases and decreases the fan speed in accordance with the cpu heat.
AnandTech
forums.anandtech.com › home › hardware and technology › cases & cooling
Fan speed constantly increasing and decreasing | AnandTech Forums: Technology, Hardware, Software, and Deals
March 25, 2018 - My fan speed is constantly increasing and decreasing. It seems that the cores are heating to 85 C and then the fans get really loud. After the temp goes back to 80 C, it quiets down. Is there any way to set a constant fan speed to somewhere in between? I know next to nothing about computers so if there's any info that you guys need please ask. ... The real question should be: why is your cpu at 80C?
Reddit
reddit.com › r/buildapc › pc fans speeding up and slowing back down?
r/buildapc on Reddit: PC Fans Speeding up and Slowing back down?
July 26, 2018 -
Hey guys, I built my PC last November and it's ran well since then but within the past few days I've noticed something that I think is a bit odd.
I bought The Witcher 3 to play when my friends aren't on or when I just want to play a good single player game. While playing, I noticed that my PC fans were speeding up and slowing down what I considered to be pretty randomly. I figured it was since I had a lot of the graphics turned up pretty high so I turned some of them down but the fans still seemed to be fluctuating in rpm's. I then noticed they were doing similar fluctuations while I was playing CS:GO, where I have all but one or two settings turned down as low as possible.
I have an NZXT kraken AIO so I checked the connections plugging in the pump to make sure they weren't loose or anything. I guess that really only leaves my GPU fans and case fans but I'm not sure what I need to do next if there is anything wrong in the first place.
My build is as follows:
Case: NZT S340 elite
CPU: Ryzen 5 1600
GPU: Asus Dual Series 1070
CPU Cooler: NZXT Kraken X62
Case Fans: stock NZXT for exhaust and stock kraken fans for intake
Edit: I usually play with headphones on so this may have started earlier but when i was playing The Witcher using my speakers is when I first noticed the fans doing this. I also had my headphones off when I was playing CS:GO and noticed it.
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Try turning on the CPU fan smoothing option in your BIOs. I've had a similar problem with a Ryzen 1700 & 2700X. Ryzen boosts, has a voltage spike, results in a temperature spike and the fans ramp up to compensate. In my case it was most noticeable at idle where light tasks (like a web browser) would make the fans ramp up for a second, which is more annoying than a consistent drone. By adjusting the CPU fan smoothing you can made the fans less 'bursty' when responding to CPU temperature spikes. You could also make your fan curve less aggressive. Alternatively you could try overclocking which disables the boost and locks at a clock speed. This thread has a bit of discussion about it.
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Fans spinning faster when components are under load is normal. Sounds like you just need to set a custom fan curve so they don't ramp up in such a quick fashion. Should be able to get a CPU & case fan curve in your BIOS. GPU fan curve with your Nvidia driver, MSI Afterburner or possible an ASUS graphics card utility?
Tom's Hardware Forum
forums.tomshardware.com › home › cpus
Question - Case fan speed increasing and decreasing randomly. | Tom's Hardware Forum
July 3, 2020 - Also, what are your CPU operating temperatures, at idle and under load? ... I've now inputted my own custom fan curve like you said but it hasn't helped. Click to expand... I just finished a B450/R5 2400g build yesterday and was annoyed with the Wraith Spire's fan ramping up and down every 8 seconds at idle. Found that the Fan Profiles in bios is the problem. I manually pushed the fan speed attack to begin at 45c and that solved that issue.
Tom's Hardware Forum
forums.tomshardware.com › home › cooling
Question - CPU Fan speed increases amd decreases | Tom's Hardware Forum
October 23, 2019 - EDIT:Forgot to mention,CPU is running at stock speeds ... Happens to me as well on my older(not using it anymore) c2q q8200 I think I did some fan settings in bios to not have big jumps in fan speed. Or set target temperature to some other temp and it could keep running more consistently.
Tom's Hardware Forum
forums.tomshardware.com › home › cpus
CPU Load and Fan Speed Fluctuating Heavily | Tom's Hardware Forum
November 3, 2011 - Here are my computer specs: Operating ... INC. P5QPL-AM Graphics AMD Radeon HD 6870 What could the reason be for this? Thanks, Amy ... The fan speed increase's when the CPU gets hotter.So whenever the CPU is maxed out at 100% usage it gets hotter....
TechSpot
techspot.com › community › topics › cpu-fan-speeds-up-and-slows-down.28199
CPU Fan Speeds up and Slows Down | TechSpot Forums
July 6, 2005 - The slow speed of the fan sounds almost like its vibrating. Not sure if that helps. Thanks. ... I would look at... I would look at a possible fan replacement, try to find some one with that fan and test it first then replace the fan if there is yar and or play that may mean you have a bent fin, shot bearing, bad bearing shoe, popped bearing, or all of the listed. if that CPU fan goes your system will make like a christmas tree in very little time after and then you are replacing the CPU heatsink as most CPUs now require you to buy the heat sink and of course the fan that died in the first place...
Quora
quora.com › Why-does-my-fan-keep-fluctuating-in-speed-by-itself
Why does my fan keep fluctuating in speed by itself? - Quora
Thermostats, temperature sensors, or CPU fan headers change speed as they read different temperatures or respond to noise in their inputs. ... Intermittent contact in plug, switch, terminal, or connector produces rapid speed changes or stuttering. ... Increased friction, uneven load, or intermittent rubbing can change load torque and ...
Reddit
reddit.com › r/buildapc › pc fans randomly speed up, even when idle
r/buildapc on Reddit: PC fans randomly speed up, even when idle
March 2, 2022 -
For the past couple of months I had this issue with my 3 year old PC where the fans randomly speed up, mostly during boot and then randomly while its idle or while Im playing. Now, Im not really sure if its just the case fans, CPU fan or both. But is it something to be concerned about?
Specs:
GPU: Asus GeForce RTX 2060 Dual Evo
CPU: Intel Core i5-9600k
MOBO: ASUS ROG Strix B360-F Gaming, S-1151
RAM: Corsair Vengeance LPX DDR4 2400mhz 2x8GB
SSD: Kingston A1000 480GB M.2
PSU: Corsair Vengeance 750M, 750W
CPU Cooler: Cooler Master Hyper H411R
CASE and case fans: Phanteks Eclipse P400 Glass, stock fans
OS: Windows 10 Home
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It's likely the setting within bios (PWM) basically giving the fans the freedom to ramp up and down depending on what your system is doing or what the temps in the case are like for the cpu. It's not an issue as such, I disable pwm and run my fans fast to reduce temps constantly.
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download speedfan and watch jayztwocents video from yt on how to set it up. It should fix your problem.
The Windows Club
thewindowsclub.com › the windows club › general › how to control fan speed on windows computers
How to control Fan Speed on Windows computers
You can either restart your PC and when it boots back up, press the ‘Delete’ and ‘F12’ keys together · Alternatively, you can follow this trajectory: Settings > Update & security > Recovery > Advanced Startup > Restart Now > Troubleshoot > Advanced options > UEFI Firmware settings > Click Restart · On the BIOS front page, locate Fan Control Settings ... Here, look for RPM settings. Once found, select the CPU fan to increase or decrease its speed with RPM as a unit
Published November 17, 2025
H|ard|Forum
hardforum.com › [h]ard|ware › overclocking & cooling
Computer lag when CPU fan changes speed. | [H]ard|Forum
October 19, 2007 - If I had to guess, and I have too, lol, the fan speed change is not what is really going on, all of a sudden your cpu sees a heavy load and the heat it generates goes up, this is the lag, the fan is just responding to the cpu load. It could be possible that the fan control software if you are using EIST or Cool n Quiet is using enough of your memory while in windows to cause a performance issue but unlikely.
Tom's Hardware Forum
forums.tomshardware.com › home › components
CPU fan speeds up for no reason, then slows down again | Tom's Hardware Forum
November 23, 2017 - Previously I had the NZXT Kraken ... Would anyone have any ideas what could be the issue? Thanks a lot, Jessica ... When the fan speeds up that generally means the CPU is generating more heat, i.e....
Cybersided
cybersided.com › home › random pc fan revving: what causes it & how to fix it
Random PC Fan Revving: What Causes It & How to Fix It
September 17, 2021 - Using a curve like this, your fan speed would be constant at 50% for about half the time or more; then occasionally when your CPU is working harder the speed would increase. It’s important that you ensure adequate cooling to your CPU when it is working harder than normal, so you may want to read more about fan curves before you start modifying yours. Read through your BIOS documentation to learn how to program your fan curve. Also, make sure you know how to monitor your CPU temperature so that you can assess whether your fan curve is providing adequate cooling.
Quora
quora.com › How-do-I-reduce-a-CPU-s-fan-speed
How to reduce a CPU’s fan speed - Quora
Answer (1 of 2): CPU fan speed is managed according to the temperature of the CPU. The temperature depends on the load on the CPU. For example, running a compute heavy application will increase the heat dissipated by the CPU, and to get rid of it, the fan will run faster. Hence, you cannot contro...
PCPartPicker
pcpartpicker.com › forums › topic › 267234-constantly-changing-fan-speed-help
Constantly changing fan speed? Help!!! - PCPartPicker
The fan speed continuously fluctuates, almost like it is pulsing. I have a few hypotheses for why this might be happening. I did not connect the CPU fan's rpm control cable to the CPU_FAN header on the motherboard. Instead I connected it to Corsair Commander Pro, and control it through the Link software instead.
Quora
quora.com › My-CPU-fan-has-been-powering-up-and-down-even-when-I-go-on-the-internet-Is-this-bad
My CPU fan has been powering up and down even when I go on the internet. Is this bad? - Quora
Answer (1 of 3): It’s Usual. When you CPU uses more power, your fan speed will increase to maintain CPU temperature. When you go on the internet, you use internet browser. Like Google Chrome or Firefox. These browsers are use high RAM and CPU even when you browse a website.
Tom's Hardware Forum
forums.tomshardware.com › home › components
CPU Fan Speed Suddenly Increased | Tom's Hardware Forum
September 10, 2012 - Fan speed spiking should not happen if the HSF is making proper contact with the CPU since the HSF will prevent the CPU from experiencing nearly instantaneous temperature spikes. Try running something like FurMark in a window and keep an eye on your monitoring tool's CPU temperature.