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Re: Failure rate of window / door magnetic sensors



Crash Gordon said:

>It happens, usually it welds the switches closed, which is why we always
>recommend the homeowner test all openings at least once a year but
>definitely after a major lightning storm nearby.  I've never found one go
>open though.

Granted, welding shut seems to be the more common failure mode.  But
sometimes, they do go open.  I think what happens is that the heat causes
the glass tube to crack where the metal reed goes through the glass,
causing it to lose its support and the spring tension that tends to keep
the switch closed.  Back in the old days, some manufacturers used gold to
plate the contacts of their reed switches.  Bad idea.



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