Block Heater

A block heater warms an engine to ease and speed starting and vehicle warmup in cold weather. The most common type is an electric heating element connected through a power cord often routed through the vehicle's grille. The block heater may replace one of the engine's core plugs, or may be installed in line with one of the radiator or heater hoses. Block heaters that run on the vehicle's own gasoline or diesel fuel supply are also available; these require no external power source. The coolant is heated and circulated, usually by thermosiphon, through the engine and the vehicle's heater core. Heaters are also available for engine oil so that warm oil can quickly circulate throughout the engine during startup. The easier starting results from warmer, less viscous engine oil and less condensation of fuel on cold metal surfaces inside the engine; thus a block heater reduces a vehicle's emission of unburned hydrocarbons and carbon monoxide; also heat is available more quickly for the passenger compartment and glass defogging.

Block heaters or coolant heaters are also found on permanently installed systems using diesel engines to allow standby generator sets to take up load quickly in an emergency.