The additional coolant pump is mounted on the heater body and is used as an auxiliary means to facilitate the flow of coolant through the FFBH and the heater radiator.
When the FFBH is active, the additional coolant pump runs continuously. When the FFBH is not running, the coolant is circulated by the engine cooling system pump. The additional coolant pump is controlled by a direct power supply from the control module to the FFBH.
Vehicles equipped with Stop/Start system
During the Stop/Start cycle, when the engine is switched off and therefore the coolant pump is not operating, it is impossible to maintain the set cabin temperature for a long time, especially at low ambient temperatures. To avoid this situation, an additional electric cooling system pump is installed, which is controlled by the ECM (engine control module) and is integrated into the cooling system to maintain the circulation of coolant through the heater radiator. This circulation maintains the set cabin temperature and, accordingly, prevents premature restart of the engine.
On vehicles with a fuel-fired auxiliary heater (FFBH), an additional coolant pump is not installed. Instead, an auxiliary coolant pump is used to circulate coolant when the engine is switched off. The pump is activated via the CJB (Central Junction Box) by the fuel-fired auxiliary heater (FFBH). For further information, refer to the chapter: Starting system (303-06C Starting system - 2.2L Duratorq - Td4, Vehicles manufactured from 03/2009 onwards, Description and function).
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