As you have figured out, the alarm
switch is the one with two wires. It is normally open, and closes when the temp is too high. It has two wires, the black is “earth” and the white/ brown connects to the alarm
wire sender is to drive a temp gauge. The resistance values and temps. are listed in the attached manual on page 28. Normally a light brown wire connects to it, and the wire can be found tucked into the harness nearby.
diagram for the engine
is on page 100.