Kysor Question?

[kingmtpg]

I have an elderly Bird with a Kysor Gauge. (The file that covers this
is missing) I have a couple of questions you experienced guys can help
me with. Should there ever be power to this guage when there is not a
engine problem? Or is the gauge powered ONLY when there is a problem.
It has only 2 wires, a ground and a hot wire. Could someone explain how
this is supposed to work? Thanks Brad Bloxham 78FC 35'3208.