T430s won't close with lid closed

[lakegeezer]

My T430s stopped sleeping when I close the lid.  Function F4 sleep mode works fine.  No Power Manager installed and Windows power option set (and remains) to sleep on lid closure.  It just won't.  My local depot replaced the system board under warranty, but that did not fix the problem.  I've also waved fridge magnets around the lid and near the touchpad, thinking that might trigger the lid sensor.  Before I send in the system to Lenovo for repair, and be without my system for another stretch of time, I'm looking to the community for other ideas.  For example, where exactly is the sensor?  thanks!

[richk]

It is to the right of center along the top of the screen. On that model, the magnet is by the right edge of the right touchpad mouse button.  It may be that the Hall Sensor (magnetic switch) is damaged, or perhaps the cable (shared with the camera and microphone) is damaged or not plugged in all the way.

[lakegeezer]

Thanks.  The mic and camera are OK, so it must be the sensor.  I am surprised that Lenovo recommended to the tech that he replace the system board, and not dig into the switch in the lid.