Swan Neck Temp Switch?

[PHart]

On replacing the bearing in my seized fan, I then set about running it, perfect. Then I went to find the otter switch, which I have, but not connected, and then realised that there is a switch welded into the swan neck which switches the fan (always wondered what it did). Looked in the bible and the swan neck pictures I found didn't have this... Anybody else got similar, or an explaniation why?

[tempus]

otters were prone to pop out when things got hot often clips were fitted help keep them in but sometimes enough is enough and similar temp screw-in fan switches were fitted sometimes into a boss but sometimes just brazed in the rad or where it would go.Tempus