Heating Circuit

Illustrated on engine 104

Function
The coolant pump (4) pumps cold coolant through the engine. There the coolant absorbs heat from the engine and is heated up. The heated coolant then flows through the heater core (5) where the heat is transferred to the interior air. The quantity of coolant flowing through the heater core (5) is controlled by the monovalve (Y19) located in the heater return (R). It is only possible to regulate the quantity of coolant for the left and right side together.

The coolant flows through the heater return (R) back to the coolant pump (4). The major portion of the coolant flows from the engine to the thermostat (3) rather than through the heater. Depending on the water temperature, the thermostat allows the water to flow to the radiator (2) or directly on to the coolant pump (4).
In the engine residual heat utilization mode, the coolant is circulated by the coolant circulation pump (M13).