No flame formation when starting heating mode, function

P83.70-0389-09

1 Burner housing

2 Heat exchanger

3 Heater circuit thermostat

A6m1 Coolant circulation pump

A6m2 Combustion air blower

Y23 Fuel metering pump

A Thermostat setting, auxiliary circuit closed - coolant short circuit

A6n1 Stationary heater/heater booster control module

A6r2 Glow pin

N22 AAC pushbutton control module

N34 Stationary heater timer

Function sequence

1 Coolant temperature:< 59 °C :
The thermostat (3) closes the auxiliary circuit and thereby the connection to the cooling and heater circuit of the vehicle.

2 The green indicator lamp on the stationary heater timer (N34) comes on. The heater start is actuated.

3 The combustion air blower (A6m2) and the coolant circulation pump (A6m1) start running. The combustion air blower operates at nearly its highest speed.

4 Coolant temperature:> 30 °C :
The AAC pushbutton and control module (N22) switches on the vehicle heater blower.

5 The flame monitor check is started for 1 s, the glow pin (A6r2) acts as a flame monitor signalling:

 "cold" = no flame  start ist continued.

6 The glow pin (A6r2) is switched on. The preglow time of approx. 30 s starts.

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7 The preglow time is terminated, the combustion air blower (A6m2) is switched off for 3 s. The fuel metering pump (Y23) starts pumping fuel.

8 The combustion air blower (A6m2) starts running. The combustion air blower and the fuel metering pump increase their speed and output to full load during the next 60 s. The fuel and the combustion air form a fuel/air mixture in the burner housing (1).

9 When the increase in the combustion air flow and fuel supply is completed, the glow pin (A6r2) is switched off and starts the safety time for the flame control for approx. 45 s:

 The glow pin acts as a flame monitor to control the flame.

10 The safety time is terminated, the glow pin indicates:

 "cold" = no flame or insufficient flame formation

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11 The stationary heater/heater booster control module (A6n1) starts the heater again once.

12 The fuel metering pump is switched off.

13 The heater shut-off delay starts purging the combustion chamber for approx. 60 s.

14 The heater shut-off delay is terminated, the flame monitor check, the preglow time and the safety time are started again.

15 The glow pin signals "cold" again.

16 The stationary heater control module (A6n1) switches the fuel metering pump off and starts a malfuncton shut-off.

17 The actuation of the vehicle blower is interrupted and the blower is switched off.

18 The heater malfunction shut-off delay for purging the combustion chamber starts for approx. 110 s. The combustion air blower reduces its speed during the first 40 s of the shut-off delay to partial load operation and then increases again to almost full load operation.

19 The malfunction shut-off delay is terminated. The combustion air blower and the coolant circulation pump switch off.

 To reset switch heater on and off again after eliminating the cause of the malfunction.