Thanks, John.
I have the second adapter that Larry posted. It just looks like the sensor that I have on my Phoenix radiator is much bigger than the threaded end of that 22mm adapter. And my radiator doesn’t have the little studs.
I need to do some more measurements.
To Mike - I don’t believe the PE temp sensor is a simple “On/Off” switch. It’s a GM sensor, and it’s probably a thermistor (variable resistance proportional to temperature).
Chuck