The supplementary heater is an option on all Multijet versions with an automatic climate control system.This device is fitted in the coolant circuit between the engine and the heat exchanger. It partly preheats the passenger compartment and engine coolant, reduces the engine warm-up time and removes ice and condensation from the windows more rapidly.In particular, the system initially heates the coolant and then, when the engine reaches normal service temperature, it is carried into the vehicle passenger compartment.The additional is turned on by the climate control system, when the user sets the climate control system to high temperatures (heating mode) and engine temperature is low.For more details: See descriptions 5020 HEATER