Unconnected black wire on fan T440P

[euless]

Hi
I was cleaning the T440P fan. And I noticed one end of a black wire is not connected to anything. It is just tucked to the side.

I found some pictures of a T440P on the internet, that showed this black wire is soldered to the case of the fan.

What is this black wire for? Does it really need to be soldered?

[axur-delmeria]

Can you post a photo of it?

[TPFanatic]

T430 fans have a similar wire that just connects to the case of the fan.

Here's a link to T440p schematics:
https://www.alisaler.com/lenovo-thinkpa ... schematic/
https://drive.google.com/file/d/15LvTsg ... ofYMo/view

Here's a screenshot of the fan connector diagram from Page 67:
https://i.postimg.cc/gcX3RD5p/t440p-fan-connector.png

ThinkPads are known for loud and noisy fans, ie. T520 had an infamous pulsing that's been mitigated by BIOS patches but still not entirely gone... whatever the extra wire is for, if it makes things in any way better, I'm glad it's there. But at the same time if the laptop works fine without it hooked up, I wouldn't bother fixing it.

[euless]

T430 fans have a similar wire that just connects to the case of the fan.

ThinkPads are known for loud and noisy fans, ie. T520 had an infamous pulsing that's been mitigated by BIOS patches but still not entirely gone... whatever the extra wire is for, if it makes things in any way better, I'm glad it's there. But at the same time if the laptop works fine without it hooked up, I wouldn't bother fixing it.

Maybe the wire is for temperature sensor?

That makes sense. The end of the wire is close to the radiator of the fan. The BIOS thermal management might need to know how hot is the radiator.

[euless]

Can you post a photo of it?

Hi, I cannot post picture. But if you do a google search "t440P fan", it will show you a bunch of photos from Amazon.
You will easily see the wire that I am talking about. It is very prominently in most of the pictures. They show a black wire sticking out.

Maybe the black wire is for temperature sensing?

On mine, it was taped to the side of the fan near the radiator.

[axur-delmeria]

https://www.pchub.com/lenovo-thinkpad-t ... xp-p178668
Like that one, on the lower left corner of the fan?

It's not connected to the motor itself, but apparently on the metal body; looks like a grounding wire to me.

[euless]

https://www.pchub.com/lenovo-thinkpad-t ... xp-p178668
Like that one, on the lower left corner of the fan?

Yes.