| A = Output of auxiliary heater (also as supplementary heater) as a % of maximum heat output |
| B = Temperature of coolant in auxiliary heater in °C |
| C = ON signal for auxiliary heater (also as supplementary heater) via convenience data bus |
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| Auxiliary heater starting sequence |
| D = Switchover to full load operation |
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| Auxiliary heater full load operation |
| E = Switchover from full load operation to control mode |
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| Auxiliary heater part load operation (control unit switches back to full load operation if coolant temperature drops below 84° C) |
| F = Switchover from control mode to run-on |
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| Auxiliary heater run-on |
| G = Start of control interval |
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| Auxiliary heater control interval |
| H = Auxiliary heater re-start from control interval |
Note | t
| If, on vehicles with heater coolant shut-off valve -N279-, the function “Incl. engine” is set in the driver information system, some of the coolant always flows via the engine in auxiliary heating mode or the heater coolant shut-off valve -N279- is not actuated by the auxiliary heater control unit -J364-. In this setting (tick against “Incl. engine”), the engine is also pre-heated at low ambient temperatures (heating of the passenger compartment then takes appropriately longer) → Chapter. |
| t
| Depending on the setting in the control unit in dash panel insert -J285-, actuation of the auxiliary heater is maintained even if the engine is started and switched off again with the auxiliary heater in operation. At a coolant temperature of approx. 91 °C, the auxiliary heater switches from control mode to control interval. If the engine is switched off on such vehicles, the auxiliary heater starts up from the control interval as soon as the coolant temperature drops below 71 °C → Chapter. |
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| Depending on ambient temperature and the quantity of heat emitted by the heat exchanger of the air conditioner/heater, the auxiliary heater may remain in the various operating statuses for a lengthy period. |
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| On vehicles with diesel engine and no electrical supplementary heater, the auxiliary heater is switched on as supplementary heater by the operating and display unit, Climatronic control unit -J255- by way of the convenience data bus system as soon as the activation conditions stored in the operating and display unit, Climatronic control unit -J255- have been fulfilled. |
| t
| If the auxiliary heater is in the control interval and receives an OFF signal via the convenience data bus system, it cuts out without run-on. If, however, the auxiliary heater is in a different operating mode at this point, the auxiliary heater control unit -J364- determines the run-on required and actuates the various components accordingly. |
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