Changing the aux belt pulley and associated spring damper I've caught a sensor on the front of the
block that only has one feed wire from it and appears to be a pressure switch with IIRC 2.5 bar
stamped on it's base. Basically the grey plastic mounting on it's head is a fussy multiplug and this
got nudged and split the plastic head off the peened brass collar on the main body revealing a single
mini piston onto a spring. I'll try and get a picture posted below;
It lives directly onto the front of the main engine block just below the diesel pump.
Anyone have one and more imminently, what does it now NOT do!?

Andrew