In our March 2013 article on external engine heaters, we noted that there is disagreement among pilots regarding keeping a heater plugged in all the time versus using it only in preparation for a flight. While we do not take sides on the matter, we note that a lot of pilots are concerned about engine corrosion caused by running an engine heater constantly, so they only want to use the heater in preparation for flight.
For those who want some way of controlling their engine heater without it running full blast all the time and don’t want to drive to the airport several hours prior to a planned cold-weather flight, there’s good news. There is not only a healthy market in remote switching units that allow firing up the heater from a distance, there is also a thermostatic control that will run your heater at an intermediate temperature.