Some sort of regulator on raw water line to the mixing elbow

[brico]

I regret I did not take the photograph of it to post but i shall next weekend. On my 1980 DD 6-71 NAs I have some sort of contraption on the raw water line going from the heat exchanger exit to the exhaust gas mixing elbow that i have no clue what it is for. It is plastic tube about 6 inches in length grey in colour and is fitted between two hoses on the raw water discharge side. There are two wires going fro some sort of a probe/sensor at the tip of he water manifold to the top of it and a square knob on the top of that piece. it looks like some sort of a flap or something that is controlled by the temperature of the water in the water manifold. What that may be?

[captddis]

Water flow sensor. Should alarm if flow is lost. It is made by Aqualarm.