Terminate heater operation function

On vehicles with CODE HZ9 (Heater booster, diesel), the heater booster (HB) heating mode is ended after a change in status from "Circuit 61 ON" to "Circuit 61 OFF" or by renewed operation of the air conditioning, heater booster, residual heat rotary switch in the climate control control and operating unit (A81) with CODE HH9 (Regulated air conditioning (Tempmatic)) or the heater booster rotary switch in the climate control control and operating unit, except CODE HH9 (Regulated air conditioning (Tempmatic)). The signal from the air conditioning, heater booster, residual heat rotary switch in the climate control control and operating unit with CODE HH9 (Regulated air conditioning (Tempmatic)) or the heater booster rotary switch in the climate control control and operating unit, except CODE HH9 (Regulated air conditioning (Tempmatic)) is sent over a discrete line to the hot water auxiliary heater control unit (E90).

 The air conditioning, heater booster, residual heat rotary switch in the climate control control and operating unit with CODE HH9 (Regulated air conditioning (Tempmatic)) or the heater booster rotary switch in the climate control control and operating unit, except CODE HH9 (Regulated air conditioning (Tempmatic)) has a "memory function" (automatic triggering of heating mode in heater booster heater unit). The "memory function" remains active until it is deactivated again by operating the air conditioning, heater booster, residual heat rotary switch in the climate control control and operating unit with CODE HH9 (Regulated air conditioning (Tempmatic)) or the heater booster rotary switch in the climate control control and operating unit, except CODE HH9 (Regulated air conditioning (Tempmatic)).

The hot water auxiliary heater control unit reads in the signal directly from the climate control control and operating unit and then interrupts actuation of the following components required for the heater booster heater unit heating mode:

 Blower motor (E90m46) of the heater booster combustion air blower, for combustion air supply

 Glow pin (E90r18), for preheating burner housing and for igniting fuel/air mixture

 Metering pump (M61), to supply the fuel

 Circulation pump (M51), for circulating the coolant

After the heating mode has been shut off, the heater booster heater unit switches to run-on mode. In run-on mode, the hot water auxiliary heater control unit actuates the blower motor for the heater booster combustion air blower and the climate control control and operating unit actuates the circulation pump so that the combustion chamber with downpipe on the heater booster heater unit is cooled down by the generated air suction and the heater booster heater unit's heat exchanger by the blowby coolant.