There are two versions of the fan/heatsink assembly. This pin is pulled low to select one version, and left pulled up to 1.8volt for the other.
I assume the different versions of the cooler have different thermal capacity, or the fans operate at different speeds, hence the firmware needing to know which is installed.
What exactly are you hoping to see on this pin?
Thanks....
Twist&TapeTechnology
New Member
Last Activity: Today, 01:00 PM
Joined: 11-29-2025
Location: SA
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Microsoft Surface Laptop 3, 1867 no fan power!
Sorry if this post ends up a bit messy, as its my first post here.
Here is a link to schematics and PCB layout files. This should make it easier to follow along at home!
https://www.badcaps.net/filedata/fetch?id=3292055
I have also attached two screenshots.
Measuring one end of C6416, I have the 5VSB rail. This is a 5v, 7.5a max rail that powers everything 5volt.
Measuring C6418 and there is no 5v. Not at the fan connector, nor at the capacitor.
However, even when the CPU gets to 80 degrees, measuring R6408, the 1k resistor... -
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