Additional Heater/Parking Heater
The additional heater/parking heater produces heat by burning gasoline. The heat is distributed via the engine cooling system to the heat exchanger and on out into passenger compartment.
When the engine is running, the additional heater can provide extra heat to the passenger compartment in the event that the engine is unable to provide sufficient heat. When the engine is not running, the parking heater can heat the passenger compartment (and the engine). This function can be started directly or using a timer.