Magnetic run indicator - GIF

[hemmjo]

Interesting, I have used a number of Grundfos pumps in several hydronic systems I have installed. They are very reliable, water lubricated.

I do wonder, if that little detector is reading magic fields are "rotating" as they do with the rotor spinning as it should. OR, if the rotor is stuck, just the magnetic fields that are trying to spin the locked rotor would cause the detector to spin, even though the rotor is locked.