Thinkpads Forum

(I tried to use image thumbnails, but it looks like imgur no longer supports that)

I've actually found the lid sensor itself, my question is: what triggers the lid sensor?

Background: I've had this T420 since 2016. I have upgraded the CPU, Wifi card, mSATA SSD, IPS display, and I replaced the old, cracked keyboard bezel/trackpad with a new one from Aliexpress. I wonder if the replacement keyboard bezel is missing a magnet or something that's supposed to trigger the lid sensor?

Here's the lid sensor. It appears to be the little black rectangle just to the right of sensor, behind the screen bezel:



Here's the area under the keyboard bezel that approximately aligns with the lid switch:



This is the area on the back side of the keyboard bezel/trackpad/touchpad that approximately aligns with the lid switch:



Is there supposed to be a magnet or something tucked in there?

Welcome to the forum.

I did succeed in converting the full-size images to large thumbnails by adding a lowercase L at the end of the file name.

I believe your guess is correct. The "keyboard bezel miscellaneous parts" FRU for T420 (04W1603) mentions a "magnet - suspend switch" pair.

See also:
viewtopic.php?t=121512

Searching for that part number (04W1603) led me to this image, which I think answers the question:



There appears to be a magnet held down by the metal strap.