71-72 speedo switch 3438494

Does anybody have any info on how this switch works? Just the switch itself. Does it turn on or off at a specific speed? Does it send a continuous signal based upon the rpm it gets from the transmission?

That's part of the NOX system, it supplies a ground signal to the control module when the road speed hits approximately 40 mph. There is also a cowl-mounted temp sensor that's part of the NOX system which retards the spark at speed.

40 mph isn't a bad. That's fast enough for converter lockup. That switch could toss the ground to a relay.

Yep, that's why I grab every one I find.