A North American block heater cord and plug. A block heater warms an engine to increase the chances that the engine will start as well as warm up the vehicle faster than it normally would in extremely cold weather.The most common type is an electric heating element in the cylinder block, connected through a power cord often routed through the vehicle's grille. block heater warms an engine to increase the chances that the engine will start as well as warm up the vehicle faster than it normally would in extremely cold weather. The most common type is an electric heating element in the cylinder block, connected through a power cord often routed through the vehicle's grille.