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

MODEL 163 

Fig 1: Identifying Heater Circuit Function

Courtesy of MERCEDES-BENZ USA

Function 

The coolant pump (5) pumps cold coolant through the engine. The coolant absorbs the engine's heat and becomes heated. The heated coolant is then conducted through the heat exchanger (2). The air blowing by the heat exchanger (2) is heated and conducted into the vehicle interior.

The coolant is routed over the coolant return (A) and the heating water circulation pump (6) back to the coolant pump (5).

By far the greater percentage of the coolant does not flow through the heat exchanger (2), but from the engine 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).