"Start heater operation, heat consumption > heat output", function

W83.70-0017-09

1 Timer
2 Control module
3 Glow pin
4 Temperature sensor
5 Burner
6 Heat exchanger
7 Overheating sensor

V Combustion air
A Exhaust
KE Coolant inlet
KA Coolant outlet
KS Fuel

8 Coolant circulation pump
9 Burner housing
10 Flame sensor
11 Combustion air blower
12 Exhaust line with muffler
13 Combustion air line
14 Fuel metering pump
15 Automatic heater control panel

W83.70-0028-01

Heat output stages

P Power

G High

M Medium

K Low

A OFF

Heat output stages

P Power

G High

M Medium

K Low

A OFF

W83.70-0029-01

Temperature thresholds with engine standing still

T Temperature in Celsius

t time

GH Switch-on threshold for blower for vehicle heater

Temperature thresholds while driving

T Temperature in Celsius

t time

GH Switch-on threshold for blower for vehicle heater

Function sequence

 The heater is switched on with the timer (1) for the auxiliary heater.

 The heater has completed the start-up phase up to the cut-off thresholds and is in one of the heat output stages "high", "medium" or "low".

 The heat consumption is higher than the current heat output of the heater. The temperature in the coolant circuit decreases.

-----------------------------------------------------------------------------------------

 The heater switches to the next higher heat output stage upon reaching one of the lower temperature thresholds.

 The temperature in the coolant circuit increases.

 The heater switches to the next lower heat output stage upon reaching one of the upper temperature thresholds.

-----------------------------------------------------------------------------------------

Heat output stages at various heat consumptions

 Heat consumption remains constant:
If the heat consumption remains constant the heater continues to alternate between two heat output stages.

 Heat consumption increases:
If the heat consumption increases the heater switches to a higher heat output stage until the coolant temperature increases.

-----------------------------------------------------------------------------------------

 Heat consumption decreases:
If the heat consumption decreases the heater switches to a lower heat output stage until the switch-off threshold is reached. The heater then switches to the cooling phase with shut-off delay before going to the controlled shut-off phase.

-----------------------------------------------------------------------------------------

Heat output stages

During the starting operation for the auxiliary heater the combustion air blower and fuel metering pump are operated at various heat output stages depending on the coolant temperature and heat consumption.

-----------------------------------------------------------------------------------------

-----------------------------------------------------------------------------------------

Heat output stages with engine standing still

 "Power" stage

Coolant temperature < 72°C

Combustion air blower = 7300 rpm

Fuel metering pump = 8 Hz

 "High" stage

Coolant temperature > 72°C < 78°C

Combustion air blower = 5600 rpm

Fuel metering pump = 6 Hz

 "Medium" stage

Coolant temperature > 78°C < 79°C

Combustion air blower = 3000 rpm

Fuel metering pump = 2.6 Hz

 "Low" stage

Coolant temperature > 79°C < 85°C

Combustion air blower = 1850 rpm

Fuel metering pump = 1 Hz

Operating state upon exceeding maximum temperature

 Cooling phase with shut-off delay

Coolant temperature > 85°C

Combustion air blower, low stage = 1850 rpm

Fuel metering pump = aus

Heat output stages while driving

 "Power" stage

Coolant temperature < 67°C

Combustion air blower = 7300 rpm

Fuel metering pump = 8 Hz

 "High" stage

Coolant temperature > 67°C < 73°C

Combustion air blower = 5600 rpm

Fuel metering pump = 6 Hz

 "Medium" stage

Coolant temperature > 73°C < 74°C

Combustion air blower = 3000 rpm

Fuel metering pump = 2.6 Hz

 "Low" stage

Coolant temperature > 74°C < 80°C

Combustion air blower = 1850 rpm

Fuel metering pump = 1 Hz

Operating state upon exceeding maximum temperature

 Cooling phase with shut-off delay

Coolant temperature > 80°C

Combustion air blower, low stage = 1850 rpm

Fuel metering pump = aus