This is were it goes:
There is a relay controlled by an oil pressure switch and a water temp switch that turns this heater on.
If there is enough oil pressure and the water temp is cold enough, then relay activates supplying power to this heater.
Once the temp gets above 160*, the temp switch opens and the relay shuts off turning the heater off.
Why Howell wants to keep it on all the time is beyond me. Even if it has a warm up mode, it doesn't keep fuel from condensing on the manifold when it's cold but once it's warm, you just don't need it anymore.