Voltage too low or too high during heating mode, function

P83.70-0393-09

1 Burner housing

2 Heat exchanger

3 Heater circuit thermostat

A6m1 Coolant circulation pump

Y23 Fuel metering pump

B Thermostat setting, open auxiliary circuit

A6m2 Combustion air blower

A6n1 Stationary heater/heater booster control module

N34 Stationary heater timer

Function sequence

1 Coolant temperature:> 59 °C :
The thermostat (3) is switched to heating mode, the stationary heater auxiliary circuit is connected to the cooling and heater circuit of the vehicle.

2 The heater operates at partial load or full load.

3 The stationary heater control module (A6n1) monitors the power supply to the stationary heater.

4 The control module recognizes a malfunction in the power supply:

 The voltage is < 10.0 - 10.5 V for more than 20 s. The control module starts a malfunction switch-off to protect the battery from being discharged.

 The voltage exceeds 15.5 V for more than 6 s. The control module starts a malfunction switch-off to protect the electric and electronic heater components.

5 The fuel metering pump (Y23) switches off thereby interrupting the combustion.

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

7 The heater malfunction shut-off delay for cooling the heater and 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.

8 The heater shut-off delay is terminated. The combustion air blower and the coolant circulation pump (A6m1) are switched off.

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