there are two different sensors - 12V => will not work with glass...
if you have the 6 - 36V (like in the link above) it should work with a 3mm glass - you will have ~1mm spare so it will be very close to the surface.
make sure the pins/cables of the connector are in the right order. Many others and I also had to correct the pins on the connector.
If you use a different mount for your sensor, make sure you have set the offset from nozzle right.
when you first home your Z with the Sensor - make sure you can kill the power quickly - if the nozzle would crash the bed or sensor is off the bed (when offset from nozzle isn't right - and yes it happened to me.)
there are two different sensors - 12V => will not work with glass...
if you have the 6 - 36V (like in the link above) it should work with a 3mm glass - you will have ~1mm spare so it will be very close to the surface.
Skynet upgrade: https://www.youtube.com/watch?v=l2B9lNi8LHE
6-36V Sensor installation: https://www.youtube.com/watch?v=uYDOZ9pUQIs