CPU fan's RPM is very slow...

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SteamyStew

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Jul 24, 2017
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A week ago maybe.. I noticed that my CPU fan made a weird noise when I booted up my computer. Like it's unstable almost... I hear a .. "chugga chugga" kinda sound that disappears after maybe 10 minutes of being turned on.

I use Asus AI Suite 3 for my fan control, and it has done its job... but I thought maybe it needed some tuning, so I pressed Fan Tuning, and afterwards I lost the ability for Extreme Quiet.. it comes up as N/A during the results. And I can't see RPM anymore on the Smart Mode screen, but rather I just see percentage of how much power the fan uses during heatup.

But even after this Fan Tuning fiasco the CPU fan still spun at a good speed, like it's supposed to.. but then I booted up today and see this.. https://i.imgur.com/i8pUWhM.png the fan is under 200RPM... Normally it's supposed to be around 600-800 when idle...

As I was writing this, the 10 minutes are over and the CPU fan is spinning like normally now, without the "chugga chugga" noise, it's running at around 600-800RPM like it normally does. What it seems to be.. is a very slow Fan Spin Up Time, even though the AI Suite has it on 2.1 seconds for spin up. Does anyone have any solutions for this slow Spin Up Time or any other solutions on what could be causing this sudden CPU Fan problem?

The CPU fan I'm using is a Corsair Hydro Series H90. It's little over 1 year old.

Thanks in advance! :D
 
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No, it won't. What you describe is a fan on its last legs! The bearings are badly worn to the point where it cannot start up normally, and it only runs slowly even when given lots of power. You REALLY need to figure out how to replace that fan as soon as you can.

On many CPU cooler systems, the fan is simply connected to the heatsink fins with screws. If that is your case, you do NOT have to replace the entire CPU cooler system. Doing the entire job can be tricky because you need to loosen the heatsink assembly from the CPU top carefully, clean off the old thermal paste residue and replace it with new, then install the new cooler system.

Instead, see if you can remove the screws that fasten the fan to the heatsink. If you can, the fan...
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SteamyStew

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I also noticed when I go into the BIOS and change the Q-fan control I'm running PWN and not DC. I see a lot of people using PWN cause it's more energy efficent? But DC gives you a constant flow of energy... so it's more stable?
 
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jesse13williamson

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While there are some changes to the suite settings as you mentioned it sounds more like the fan itself starting to die or at least slow down. If you can try changing the fan to see if the behaviour persists. If you have any more questions the I’d be happy to help.
 
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SteamyStew

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Thanks for the reply!
Sadly I don't have another CPU fan to try out... But today when I booted up my computer the fan refused to spin. It span up for a few seconds then died. I ended up going into the BIOS and changing the power settings from PWM to DC and now it spins like no ones business. Only downside is that it's gonna use a little more power from now on. Hopefully it'll keep spinning for a long time.
 
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Paperdoc

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No, it won't. What you describe is a fan on its last legs! The bearings are badly worn to the point where it cannot start up normally, and it only runs slowly even when given lots of power. You REALLY need to figure out how to replace that fan as soon as you can.

On many CPU cooler systems, the fan is simply connected to the heatsink fins with screws. If that is your case, you do NOT have to replace the entire CPU cooler system. Doing the entire job can be tricky because you need to loosen the heatsink assembly from the CPU top carefully, clean off the old thermal paste residue and replace it with new, then install the new cooler system.

Instead, see if you can remove the screws that fasten the fan to the heatsink. If you can, the fan itself will be a standard computer fan with two particular features you need to pay attention to in choosing a replacement. It should be of the "Pressure" type, not the "Flow" type, so it can blow well through the fine spaces of the heatsink. Plus, I recommend you choose a 4-pin fan type, not 3-pin. And of course it should be the same physical size - often 80 mm, sometime larger.

Before installing the new one, examine carefully the heatsink once the old fan is off. If there is substantial dust accumulated between the fins, gently remove all of that to ensure good air flow with the new fan.

FYI, there are two fundamental fan designs in use now. The older 3-pin fans can only have their speed controlled by Voltage Control Mode (aka DC Mode). The newer 4-pin fans prefer PWM Mode, although they CAN be controlled by DC Mode. It is always best to match the fan design you have to the Mode of speed control configured for that fan header in BIOS Setup. If you connect a 3-pin fan to a mobo header that uses PWM Mode, it cannot have its speed controlled - it will always run full speed. That is exactly what you describe in your last post. You changed the CPU_FAN header to use PWM Mode and the fan now runs fast and at fixed speed. That is, given full power, it can run, even though its bearings are failing. But that cannot continue - it will fail again! Replace the fan.
 
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