| Functional description of auxiliary heater |
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| Activate/deactivate the auxiliary heater via the MMI (Multi Media Interface) or using remote control. |
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| If the “auxiliary heating/auxiliary ventilation” function has been set with the MMI (Multi Media Interface) by way of the “timer” function or if auxiliary heating/auxiliary ventilation is activated via remote control, the air conditioner operating and display unit, Climatronic control unit -J255- determines on the basis of the set “specified temperatures” and the measured “actual temperature” whether the “auxiliary heater” is switched on or only the “auxiliary ventilation” function is activated. |
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| Depending on the amount of heat generated in the auxiliary heater (and by the engine) and emitted by the heat exchanger of the air conditioner unit, the heater (auxiliary heater) may remain for a lengthy period in full load, part load (control mode) or control interval status. |
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| To ensure optimum combustion in the heater, the metering pump -V54- (clock frequency) and combustion air blower -V6- (voltage) are regulated over the entire sequence. |
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| If the heater has been interlocked on account of a fault, the event recorder must be read out and the content of the fault memory erased. Depending on the cause of the fault, it may also be necessary to cancel the interlock by way of the “Adaption” function. |
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| If the first attempted start does not produce a flame, the supplementary heater control unit -J364- terminates the sequence and attempts another start after any combustion residue has been blown out with the combustion air blower -V6-. The supplementary heater control unit -J364- is deactivated if repeated starting also fails to produce a flame. The heater is disabled after 3 manual attempted starts with start repetition in each case by way of the operating and display unit, Climatronic control unit -J255-. |
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| If the heater is switched off during the starting process, the heater is either immediately deactivated or switches to run-on mode (burn-off, cooling) if necessary, depending on the point reached in the starting sequence. |
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| If the coolant temperature exceeds 89 °C prior to attaining full load mode (e.g. with a hot engine), the heater switches to the control interval. |
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| Various auxiliary heater functions are constantly monitored during operation (the auxiliary heater is switched off as soon as a fault occurs). |
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| The auxiliary heater operating sequence can be monitored by way of the vehicle diagnostic, testing and information system -VAS 5051/- (“Reading measured value block” function). |
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| The temperatures given in the sequence of operations and function diagram are approximate. The actual temperatures at which the various functions are activated and deactivated may differ depending on the vehicle model and characteristic curves stored in the supplementary heater control unit -J364-. |
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| Sequence with required heat output between 50 and 100 % → Chapter. |
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| Sequence with required heat output less than 50 % → Chapter. |
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| Actuation of heater coolant shut-off valve -N279- → Chapter. |
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