Heating circuit, function - GF83.20-P-2003B

MODEL 140 as of 1.9.95 

Fig 1: Heating Circuit Function Diagram - Illustrated On Engine 104

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Illustrated on engine 104 

On vehicles with rear air conditioning (code 582) 

Function 

The coolant pump (4) pumps cold coolant through the engine.

There, the coolant absorbs heat from the engine and is heated up.

Then the heated coolant 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 duovalves (A31y1 and A31y2) located in the heater return (R). The quantity of coolant can be regulated separately for the left and right side. The coolant travels 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) and not 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).

On vehicles with rear air conditioning (code 582) 

On vehicles with rear air conditioning (code 582) heated coolant is also fed to the heater core (6) in the rear. The quantity of coolant flowing through the rear heater core (6) is controlled by the duovalves (A31/1y1 and A31/1y2) located in the heater return (R). The quantity of coolant can also be regulated separately for the left and right sides.