Switching Between Heating/Stationary Ventilation

Switching Between Heating/Stationary Ventilation, Function

Shown On Models 215, 220:

Operating procedure
1 The STH heater or heater booster (A6) operates in partial load or full load mode:
- The green or red indicator lamp in the STH switch (N72s12 or S46) illuminates.
- The coolant heated in the STH or heater booster heater (A6) flows through the heating and cooling circuit.
- Coolant temperature > 30 degrees C and < 72 degrees C:
The ventilation blower, initialized by the operating and control module (N18, N22 or N22/7), feeds pre-heated air into the interior.

2 The interior temperature exceeds the temperature value preset at the operating and control module (N18, N22 or N22/7).

3 The operating and control module (N18, N22 or N22/7) transmits the "Ventilate" signal to the STH or heater booster control module (A6n1) via the CAN Class B (CAN-B).

4 The STH or heater booster control module (A6n1) initializes heater delayed switch-off to cool the STH or heater booster heater (A6) and to flush the combustion chamber out:

NOTE: The duration of the heater delayed switch-off is oriented towards the existing operating condition:
- Partial load operation approx. 160 s
- Full load operation approx. 170 s

5 The ventilation blower now feeds air into the interior without pre-heating.
- The green or red malfunction indicator lamp in the STH switch (N72s12 or S46) indicates that stationary ventilation is active by flashing on and off.
- The in-car temperature falls or remains constant.

6 The interior temperature drops below the temperature value preset at the operating and control module (N18, N22 or N22/7).

7 The operating and control module (N18, N22 or N22/7) transmits the "Heat" signal to the STH or heater booster control module (A6n1) via the CAN Class B (CAN-B).

8 Heater operation is restarted by the STH or heater booster control module (A6n1):
- The green or red indicator lamp in the STH switch (N72s12 or S46) is switched back to steady light again.

9 After combustion has become stable, pre-heated air is again supplied to the interior via the vehicle blower.

NOTE: During a heating period, repeated switch between stationary ventilation and heating can occur, depending on temperature behavior.