Heater circuit function - GF83.20-P-2003Q

MODEL 209.3 /4 

Fig 1: Heater Circuit Function

Function 

The coolant pump (5) pumps cold coolant through the engine (M). The coolant absorbs the engine's heat and becomes heated. After this the heated-up coolant is routed through the heater heat exchanger (8) where the heat is given up to the interior air

The coolant constantly flows through the heater heat exchanger (8).

The control, depending on the temperature desired in the vehicle interior, is carried out via the blending air flaps, which are activated separately for the left and right side via the left and right blending air flap actuator motors.

The coolant returns to the coolant pump (5) via the coolant return (A), in which the coolant circulation pump (on vehicles with code (670a) residual engine heat utilization system MRA and code (581b) comfort automatic air conditioning) is located. By far the larger part of the coolant does not flow through the heater, but from the engine (M) to the coolant thermostat (4). Depending on the water temperature, this conducts the water through the radiator (3) or directly to the coolant pump (5).

In addition a heater booster is fitted to vehicles with diesel engines. This heater booster is required to compensate for the heat output deficit occurring under certain operating conditions (partial load).