The magnetic key switch on my old Proform 345 treadmill is broken. Unfortunately, I have never seen one that isn't broken for comparison.

For more context, there is a small metal piece that appears to mount to the front of the control panel, over the upper control board. This piece of metal currently does not stay in place.
Due to its shape and mounting position, as well as the positioning of some open testpoints or vias directly below it, I had thought that the magnetic key switch worked by magnetically pulling the metal plate up off of the vias.
Now I am thinking that is silly, and the metal piece is just there to secure the magnet key in place so that a reed switch below it can close.

Is the latter explanation correct? If so, then that means I can just secure the metal piece to where it goes and not worry about it having to be able to move at all.
I realize I could determine this experimentally, but it's a fairly lengthy process to disassemble and reassemble at this level, so I thought I would ask first.
Thank you very much!

 

Welcome to AAC.

Although I don't know that particular treadmill, it is most likely there is a a Hall effect sensor mounted to the PCB directly below the magnet. The only other likely answer is a reed switch, like the kind used in alarm door sensors.

The hall sensors could be anything from what looks like a plastic-case transistor to a surface mount device while the reed switch would most likely benefit an left of exposed contacts in a tiny glass tube.

 

If the sensor SW is 2 wire and operated by a magnet, then you most likely have the magnetic reed switch version.
These were the most common TM versions.