Doug White wrote in
:

I took apart the original switch that died. The construction inside is
very different from the typical ones with a phenolic board. The C&K is
molded plastic, and the contacts are to the side of the switch slider,
rather than underneath. The contacts didn't look pitted or worn, but
there was some green corrosion. The design looks like it should provide
a good wiping action, but the force is supplied by a wimpy little coil
spring. I suspect that the corrosion built up to the point where the
feeble wiping force couldn't reliably break through the crud. I had
tried sliding it back & forth to scrub the contacts, but that didn't do
it. I don't know if the spring is too weak to start with, or maybe took
a compression set over time.

The DPDT CW brand switch with the threaded holes installed very nicely,
and with the contacts doubled up, it should last a long time. Not
having to mess with pop rivets means it will be trivial to replace if I
ever need to.

Thanks for all the input & discussion.

Doug White