If a locomotive is not equipped with winter isolate, what should the throttle be set at when unattended in freezing temperatures?

When a locomotive is not equipped with winter isolate and is left unattended in freezing temperatures, setting the throttle to "Run 3 - no load" is essential for maintaining adequate heat within the locomotive's engine and systems. At this throttle setting, the engine can generate enough heat to prevent fuel components and other critical areas from freezing.

Operating at "Run 3 - no load" keeps the engines running and maintains the necessary temperature to ensure that fluids, such as fuel and oil, do not thicken or congeal due to the cold, which could lead to operational issues when the locomotive is needed again.

Choosing a lower throttle setting, such as shut down, would not provide enough heat to prevent freezing issues, and higher throttle settings like "Run 1" or "Run 2" could unnecessarily increase fuel consumption without significantly improving the heating effect needed in extremely cold conditions.