The independent heater (SH) is an integral part of the integrated heating and air-conditioning system. The SH provides heat output inside the vehicle that is not dependent on the engine. The control unit is fitted directly on the heater. Communication in the overall vehicle takes place by means of K-CAN telegrams based on KWP 2000. The SH takes over activation of the components necessary for operation shown in the brief description of components.
The function of the SH control unit must be ensured when the voltage supply is applied. The activation (switching on and off) always takes place in normal operation via K CAN telegram. The control unit is the central component and it communicates alongside the independent heating components with the DME/DDE, the CAS, the IHKA and the instrument cluster, which jointly ensure the correct operating mode of the independent heating. The control unit consists of the control unit, the temperature sensor, the overheating protection, the heat conductor and the connecting strip. The control unit is vented by the combustion-air chamber of the burner via an air hose. Together with the burner housing, the control unit forms a single unit and must not be disassembled.
The burner housing contains a coolant inlet and outlet and the exhaust-gas outlet connection. The burner housing accommodates the burner insert and together with the control unit forms a single unit.
The combustion-air fan unit contains the combustion-air fan, the opening for the fuel line and the opening for the fuel supply connection. The combustion-air fan delivers the air needed for combustion to the burner insert.
The fuel is distributed in the burner tube in the burner insert. Combustion of the fuel/air mixture takes place in the burner tube.
The heater plug/flame monitor located in the burner insert ignites the fuel-air mixture when the heater is started. After starting, heater plug/flame monitor takes on the task of the flame monitor. The heater plug/flame monitor is an electrical resistor. When the heater plug/flame monitor is active, there is cyclical static monitoring of the heater plug resistance. -> Heater-filament breakage detection.
The circulation pump is attached to the combustion air blower unit. The circulation pump ensures a flow of coolant in the vehicle/heater circuit. The pump is activated by the control unit and runs throughout the entire operation of the independent heater. In the event of repairs, the circulation pump can be replaced separately.
The metering pump serves to supply the fuel from the vehicle's fuel tank. In the event of repairs, the metering pump can be replaced separately.
The changeover valve switches between two separate water circuits: the engine coolant circuit and the independent heater circuit. At zero current, the changeover valve is set to the engine coolant circuit. In the event of repairs, the changeover valve can be replaced separately.
The independent/auxiliary heater is an integral part of the IHKA integrated heating and air-conditioning system. The IHKA controls the independent/auxiliary heater in all operating modes.
The Digital Motor/Diesel Electronics DME/DDE transmits cyclically every 200 ms the engine operating state engine on or off, which is evaluated by the auxiliary/independent heater.
The Car Access System CAS transmits cyclically every 500 ms the terminal status e.g. terminal R, terminal 15, which is evaluated by the independent/auxiliary heater.
The Central Gateway Module (ZGM) connects the byteflight, K-CAN, PT-CAN data buses and the diagnostic bus.
The independent-heating functions are activated by pressing the buttons on the remote control. In turn, the functions are actually executed by means of IHKA telegrams to the auxiliary/independent heater.
Implausibility
When criteria are identified which call for the independent heater to be deactivated, it is first necessary to wait for the IHKA OFF command. Therefore, in this case, the independent heater starts a codable timer (default value: 10 seconds) within which the signal IHKA OFF must come. If it does not come, the independent/auxiliary heater switches off automatically and sends its status ”Off due to implausible operating mode”. This must be acknowledged by the IHKA (integrated automatic heating / air conditioning system) to enable a new start.
For independent heating, the outside temperature must lie below 16°C in the case of preselected switching time. Direct switching on via the Control Display is possible at all times.
Switch-on conditions (each of the following points must be satisfied - AND condition)
Switch-off conditions (each of the following points necessitates switching off of the independent-heating procedure or prevents switching on - OR condition)
Implausibilities / criteria (each of the following points necessitates switching off of the independent-heating procedure - OR condition)
Overheating lock
In the event of a temperature-control failure or partial overheating, e.g. as a result of a lack of water, the overheating protection switches off the independent/auxiliary heater permanently. If the overheating lock is activated, an entry is made in the fault memory of the independent/auxiliary heater.
Heater lock
The independent/auxiliary heater is permanently locked if three malfunctions or three faults relevant to operation have occurred in sequence - i.e. without correct operation in between. For example, lack of fuel on a number of occasions could lead to failure to generate a flame. Here, the heater lock is activated, which leads to an entry in the fault code memory of independent/auxiliary heater. This fault is not identical to the overheating lock fault.
Fault
The fault lockout occurs when a fault is detected during operation and the independent/auxiliary heater switches off.
Restart
Country versions
No country versions present.
Coding versions
The independent/auxiliary heater is coded once at the factory. A distinction is made between petrol and diesel coded independent/auxiliary heaters. The independent/auxiliary heater cannot be coded in the dealer organisation.