I'm helping somebody who has some issues with a Northern Lights
genset. It shuts down for over temperature. It's probably the thermostat but while troubleshooting, I decided to test the 95C temperature switch and a spare he has using a pot of water
on the stove with thermometer and multimeter. I noticed that there is a wax-like substace used as an insulator and there seem to be some "windows" in the housing to check it. This wax is dark red on the old switch and light beige on the new one.
Is this some kind of indicator?