GF83.20-D-2003HT Heater Circuit Function

GF83.20-D-2003HT Heater Circuit Function

- with CODE (HH9) "Tempmatic" regulated air conditioning

On vehicles with code (HH9) Regulated air conditioning (Tempmatic), the circulation pump (M13/4) for the engine residual heat utilization function is installed up to August 31, 2008. As of September 1, 2008, the circulation pump is only available if one of the following special equipment packages is also installed:
- Code (HZ5) 10 kW auxiliary water heater with timer
- Code (HZ9) Heater booster, diesel
- Code (H12) Auxiliary heater (warm water)
- Code (H13) Additional heat exchanger in cargo area







16 Front heater heat exchanger
21 Coolant expansion reservoir
22 Water pump
23 Coolant thermostat
24 Radiator
A Heater return
B Heater feed
C Vent line
D Coolant feed
E Coolant return flow
M Engine
M13/4 Circulation pump

The heating circuit is connected to the engine's cooling circuit.
The following components are connected to the cooling circuit:
- Coolant expansion reservoir
- Water pump
- Coolant thermostat
- Radiator
- Engine

The front heater heat exchanger and the circulation pump are connected to the heater circuit.
The cooling circuit is divided into the following sections:
- Coolant feed
- Coolant return
- Heater feed
- Heater return
- Vent line

During the warm-up phase and normal operation of the engine, the coolant is delivered to the engine coolant guides by the water pump via the coolant feed. The coolant is heated up in the engine coolant guides. The coolant thermostat remains closed as long as a certain coolant temperature has not yet been reached. When the coolant thermostat is closed, a small amount of coolant reaches the front heater heat exchanger via the circulation pump integrated into the heating water feed. The coolant flows from the front heater heat exchanger through the heating water return back into the coolant feed. The rest of the coolant flows from the closed coolant thermostat to the radiator via the coolant return and from there, back to the coolant feed via the water pump.
Once the coolant has reached a certain temperature, the coolant thermostat opens and a fixed quantity of coolant is supplied to the front heater heat exchanger by means of the circulation pump integrated in the heating water feed. The coolant is delivered back into the coolant feed from the front heater heat exchanger via the heating water return.
A fixed quantity of coolant is also delivered to the radiator via the coolant return and from there, back to the coolant feed via the water pump.
The coolant expansion reservoir compensates for any coolant losses in the cooling circuit via the coolant feed and keeps the heated coolant at a constant pressure.
Excess coolant flows from the radiator back to the coolant expansion reservoir via the vent line.