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CPU fan error: common causes and how to fix them

This error is put in place to help you protect your CPU and socket. But why are you seeing it and what should you do about it?

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CPU fan error warning is a feature built into most motherboards to help you protect against damage caused by excessive heat. Not only does it protect the CPU but it also protects the socket too. As a CPU heat surge is not only detrimental to the CPU but also the socket it sits in. This is arguably the most important fundamental failsafe your PC has, but why are you seeing the error?

CPU fan error on boot? What is it?

cpu fan error

The CPU fan error is designed to trigger when the PC cannot detect a fan or device connected to the CPU-fan fan header. This fan header is unique to all the others in the way that it has this failsafe tied directly to it. This only ever serves one purpose and that is to protect your CPU from thermal harm.

If the motherboard does not detect a device connected to the fan header or the motherboard detects anomalies within the device connected to the fan header, then the motherboard will throw up this error just after post.

The reason your motherboard will refuse to boot into your OS is due to the fact that Windows and other GUI-based operating systems take some amount of CPU load to sustain. Any amount of load on an uncooled unregulated CPU would lead to rapid temperature climbs and eventually an emergency shutdown. It’s this rapid climb and high sustained temperature that the CPU fan error seeks to prevent.

Why am I seeing the CPU fan error?

Using what we know about the CPU fan error we can make some deductions around what the issue may be in your PC. There are a few possible causes we can explore, some are simple to diagnose but others aren’t. Let’s take a look at some of the simpler issues first.

CPU fan error diagnosis.

We’re going to take a dive into the world of diagnostics and try to deduce what may be going
on to cause the CPU fan error.

cpu fan error

CPU fan header connection

First off, let’s cover the basics. Check and make sure your cooling device of choice is correctly connected to the CPU fan header. Ensure it’s connected fully, not offset by any amount of pins, and pushed all the way to the bottom of the connector.

We can’t tell you how many times we have built a brand new gaming rig and forgot to plug in something important like the CPU fan header. It happens to the best of us and it’s nothing to be ashamed of.

Device fault

Having the CPU fan error display can be demoralizing, especially when everything appears to be connected properly. But you’ll be happy (or unhappy) to know that it’s not always your fault.

The sad truth is that devices fail eventually. It might not be today, tomorrow, or even in five years’ time, but they will. And when that happens to a cooling device it has been known to prompt the CPU fan header. There are three main types of cooling (Air, AIO, and Loop). We’re going to outline a really simple observation to note so you can make an educated decision around device fault.

Air – Check to see if the fan connected to your CPU fan header is spinning properly and doesn’t seem to be slow or meeting any resistance.

AIO – A little trickier, but you will be able to hear your AIO pump engage, accompanied with an audible water ‘sloshing’ sound within the first few seconds of the PC being powered on.

Loops – This applies to both full loops and CPU loops only. Check to see if the water in your loop is moving. It helps if you have a flow meter attached to check the flow with ease but if not, a simple visual check should suffice.

cpu fan error fault

Pump tip – your pump will tell you when it’s on its way out or if it’s suffered damage of any kind. Pumps (whether in AIOs or loops) tend to whirr when they aren’t feeling too well and you will observe this as a high-pitched whine. It’s annoying and hard to miss but it’s sometimes mistaken as coil whine from a PSU, but that is a different issue entirely.

If you observe any one of these systems outlined not working correctly then it’s more than likely your device is at fault.
The only time a device can cause the CPU fan error is when that device is plugged directly into the CPU fan header on your motherboard. You don’t need to check any other devices.

Motherboard fault

After going through all of that it is entirely possible that your motherboard or the CPU fan header itself is in fact faulty. If you’re adamant there’s nothing at all wrong with your cooling solution then it could be your motherboard.

Your best bet is to RMA your motherboard if you’re still within your warranty period before attempting repairs of any kind. There’s an easy way to get past this if you don’t fancy sidelining your PC for a few weeks. We’ll get to that now.

Disable the CPU fan warning

Disabling the CPU fan warning is one solution we recommend only with extreme caution. If you happen to be incorrect about your cooling solution being fully operational you run the risk of causing serious damage to your CPU and/or your CPU socket.

With all the warnings out of the way, disabling the CPU fan error is a simple endeavor but is slightly different depending on the manufacturer of your motherboard.

Within your motherboard BIOS in the advanced settings you should see a monitoring tab. In there you will see an option similar to ‘CPU fan speed’ or ‘CPU fan error’. Change to either ‘ignore’ or ‘disable’ and you’re good to go. This tutorial was modeled on a modern ASUS BIOS but it won’t be too dissimilar on other boards.

bios fan speed ignore Screenshot 2022 01 27 09 13 04

Once the speed warning has been disabled the PC will no longer check for a CPU fan during POST.

Monitor your temps

Whether you choose to disable your CPU fan check, the first thing we recommend is heading into the BIOS to check temperatures. If everything seems normal, only then would we boot into our OS of choice and monitor temperatures there. If you see abnormal spikes of any kind, kill the power. You’re now essentially a human CPU fan checker.

Final word

The CPU fan error is an integral part of the POST process your PC performs upon startup. Without it, thousands of CPUs would be damaged needlessly to unsafe operating temperatures.
PC diagnostics can be tricky, especially when the problems occurring aren’t always physical. The CPU fan error is no different, but now you’re armed with the knowledge you need to tackle this issue in a safe way.

Did you know WePC runs it’s own subreddit for CPUs? You’re all welcome here in r/CentralProcessingUnit

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Jack Howarth

Jack has been interested in computers and tech since 10 years old when he decided to dismantle his PC to see how it worked. Ever since Jack has had a passion for IT and gaming beyond any other. He loves the data and testing process and allowing himself to take an analytical and technical approach to PC hardware. He's even gone as far as getting educated in cyber security.

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