What Is a Circulating Block Heater?

A circulating block heater is a device that circulates engine coolant through the engine block, radiator and other cooling system components while the vehicle is not in use. In cold climates, the block heater allows easier starts, immediate use of the heater and protection from frozen drive train components.

The circulating block heater is commonly installed on the water outlet, and it consists of a small electric pump, a heater and an AC connection. The AC plug is mounted near the grill of the vehicle and connected to a standard outlet when the vehicle is parked, keeping the engine coolant warmed to a preset temperature.