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Problem

When i touch the left underside of the laptop the fan speed goes up drastically

Other than in this situation, the fans almost never spin up (unless i run something like a 3d game or do heavy computation)

I suspect this is because of a temperature sensor, but i'm not sure

This was not a problem when the laptop was new, but i'm not sure when it started to happen

The same thing happens on XUbuntu 22.04 and on Windows 10

What i've tried

On Xubuntu

I've compared outputs of sensors -u when the fan speed is normal and high (because of touching the left underside of the laptop), and i cannot see much of a difference. No temperature is ever higher than 39 degrees C here

There's more sensor/temperature info in hardinfo and some values up to 48 degrees C but still not much of a difference when i compare when the fan speed is normal or high

I've run sudo sensors-detect and followed the defaults, except for the last one where i chose to add coretemp to /etc/modules. After restart sudo pwmconfig unfortunately gives the following: /usr/sbin/pwmconfig: There are no pwm-capable sensor modules installed

On Windows

I've installed HP's Command Center, and set the profile to "Silent", but there was no difference

Question

How can i avoid the problem of high fan speed when touching the left underside of the laptop?

Idea: Maybe if i could disable a sensor somehow that could solve this problem. (I don't know which sensor that would be though since i haven't been able to find a real difference in values)

My system

Hardware:

  • HP laptop Model 14-cf2826no
  • i5-10210U @1.60 GHz
  • 8GB RAM

OS:

  • XUbuntu 22.04 LTS
  • Windows 10

Update: Added the model of the laptop

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6
  • By "touch", do you mean "touch slightly" or "press" ?
    – harrymc
    Commented Apr 25, 2023 at 17:43
  • I don't have to press, just touch it with my hand or have it on my lap. If the laptop is on a plain surface though it's fine usually
    – sunyata
    Commented Apr 25, 2023 at 18:12
  • Doesn't sound at all like a temperature sensor problem. Perhaps an electric one. Is the laptop's body made of metal, or at least where you touch there is a metallic element?
    – harrymc
    Commented Apr 25, 2023 at 19:11
  • The body is made of plastic only. I can share a picture if that would help?
    – sunyata
    Commented Apr 26, 2023 at 11:01
  • Is the reaction to the touch immediate?
    – harrymc
    Commented Apr 26, 2023 at 13:40

3 Answers 3

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1

According to the manual, you are placing your hand directly over the battery (19) :

enter image description here

This seems to me like an electric field phenomena.

You might have an repair-shop look at your laptop, but I don't think that we can give here a solution.

Software-wise, the most we can advise is to use software that controls the speed of the fans, such as SpeedFan or its alternatives.

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2
  • Thank you for looking into this! So if i understand the problem could be that there is an electric field phenomenon which starts the fan directly (bypassing the sensors), is that right?
    – sunyata
    Commented Apr 27, 2023 at 18:26
  • 1
    I admit it's a weird theory, but according what you say I can't think of any reason why just slightly touching would cause it. I also thought of electrical static buildup in the computer, but because the bottom is plastic, this doesn't seem likely.
    – harrymc
    Commented Apr 27, 2023 at 18:40
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To know for sure I would need to know the HP model but because you indicated the fan increases tells me that you should have vents for airflow. Look to see if the vents are on the left side where you are placing your hand. If you could place your hand in the same position in the past and it has changed now it could be due to dust collecting on the fan.

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2
  • I found this on the underside of my laptop: Model 14-cf2826no, and I've updated the question with this info
    – sunyata
    Commented Apr 25, 2023 at 18:10
  • As it’s currently written, your answer is unclear. Please edit to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers in the help center.
    – Community Bot
    Commented Apr 25, 2023 at 18:24
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I've now managed to solve this issue. First i removed the back cover of the laptop, using the manual that @harrymc linked to, and saw that one of the four wires for the fan was damaged.

It turns out that the wire was sticking up a bit and when i touched the left underside of the laptop the cable came in such a position that it didn't transfer electricity and the fan started spinning at the highest level

Why it went to the highest level and didn't stop i'm not sure, but from what i've been able to find the blue cable for laptop fans is used in PWM (pulse width modulation) mode to determine the speed of the fan, and i guess the relationship is inverted, so less electrical signals means higher fan speed

So i went to a repair shop which fixed this wire for me, only cost 200 SEK (20 euros, 20 US dollars)

Overview photo after removing the back cover

laptop-underside

Detail photo of damaged fan wire

detail-fan-cables

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