Heater control with auxiliary heater, function

W83.20-0002-09

1 Motor

2 Transmission

3 Coolant pump

4 Coolant thermostat

5 Radiator

6 Thermostat

7 Heater return

8 Filling volume

9 Expansion volume

10 Additional volume

11 Filler neck

12 Pressure relief valve 1

13 Pressure relief valve 2

14 Heat exchanger

15 Heater solenoid

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16 Timer (auxiliary heater)

17 Operating unit

18 Heat exchanger sensor

19 Outside temperature sensor

20 Interior temperature sensor

21 Auxiliary warm water heater

22 Driver's cab heating/engine preheating switch

23 Engine preheating solenoid valve

24 Check valve

25 Check valve

A Standard coolant circuit

B Coolant circuit for auxiliary warm water heater

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Task

The task is to manually set and electronically regulate the temperature of the cab interior, whereby the various influencing variables (outside temperature, interior temperature, heat exchanger temperature) are considered. Additionally, during the cold season, and before starting a journey, a pleasant temperature-controlled interior or windows free of ice and non-fogging can be provided by the warm water auxiliary heater.

Function

The coolant pump (3) pumps "cold" coolant through the engine block.

Finally it passes through the warm water auxiliary heater (21) and reaches the front heater in a heated-up state.

Here, a heat exchanger (14) is used to deliver heat to the cab air.

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The heater solenoid (15), which is electronically regulated by the control (17), is used to periodically interrupt the flow of coolant and thus regulate the coolant flow through the heat exchanger. The heater solenoid (15) is actuated by way of a specified-value potentiometer from the temperature setting rotary switch.

The coolant returns back to the coolant pump (3) via the heater return (7). It is mixed beforehand with cooled coolant from the radiator (5). By far the larger part of the coolant does not flow through the heater, but from the engine to the coolant thermostat (4). Depending on the water temperature, this conveys the coolant through the radiator (5) or directly to the coolant pump (3).

In stationary heater mode the warm water auxiliary heater (21) is activated using the time switch (16) (direct switch-on or timer). The "engine preheating" (22) switch can be used to preheat the engine instead of the interior.

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