We're seeing some failures (about 0.1%) of reed switches we use (Hamlin59045-T). They seem so get stuck in closed position in some cases. The switches are used to activate the device from outside the waterproof case with a keyfob magnet.
The circuit has a 1M||100nF pulldown+filter and reed switch from there to +2.8VDC.
I'm now wondering what is going on. Some ideas are:
-Too strong magnets used for activating the devices
-Welding of contacts (with 100nF 2.8V ?!)
-Moisture destroying something (supposed to be hermetic glass!)
Sometimes the switch can be opened by knocking it, sometimes not. The reed switch is moulded in plastic, so opening it up typically causes enough mechanical vibration to destroy the fault before getting there.
Any ideas what could be the culprit ?