| Checking electric supplementary heater |
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| Vehicles with diesel engine are currently fitted with an electric supplementary heater (heat energy is added to the air flow immediately after exiting from the air conditioner unit heat exchanger). → Audi Sales Range |
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| Vehicles with diesel engine and “auxiliary heater” as optional extra may not be fitted with an electric supplementary heater depending on the vehicle control system. On such vehicles, this function is assumed by the auxiliary heater, which operates as a fuel-driven supplementary heater (by adding additional heat energy to the coolant). → Audi Sales Range and → Auxiliary heating. |
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| Vehicles with petrol engine are not fitted with a supplementary heater at present. |
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| On vehicles with electric supplementary heater, the operating and display unit, Climatronic control unit -J255- actuates the engine control unit by way of the convenience data bus system (the control unit in dash panel insert -J285- is the interface between the convenience and drive data bus systems). This then decides whether the auxiliary heater element -Z35- is activated. Depending on the version of the engine control unit, an indication is given in various engine control unit measured value blocks of the reason for the auxiliary heater element -Z35- not being activated or being actuated. → Diesel direct injection and glow plug system; Rep. Gr.01 |
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| The operating and display unit, Climatronic control unit -J255- transmits the request for electric supplementary heater activation via the data bus system to the engine control unit (and to the auxiliary heater control unit -J364-): |
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| - If the operating and display unit, Climatronic control unit -J255- is encoded for a diesel engine (not absolutely essential depending on version of operating and display unit, Climatronic control unit -J255-). |
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| - If the operating and display unit, Climatronic control unit -J255- is not in “Econ” or “Off” mode. |
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| - If the ambient temperature determined is less than 5 °C or has been at least once since switching on ignition. |
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| If the specified vent outflow temperature calculated by the operating and display unit, Climatronic control unit -J255- has been greater than 45 °C and is still greater than 40 °C. |
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| - If the coolant temperature transmitted by the control unit in dash panel insert -J285- and calculated by the operating and display unit, Climatronic control unit -J255- is less than 70 °C (under certain conditions less than 80 °C). |
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| The electric supplementary heater is only switched in for example by the diesel direct injection system control unit -J248- if certain conditions are simultaneously fulfilled. → Diesel direct injection and glow plug system; Rep. Gr.01 The engine control unit switches on the supplementary heater if the following requirements are fulfilled |
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| - The operating and display unit, Climatronic control unit -J255- transmits a request via the data bus system. |
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| The engine speed is in excess of 600 rpm. |
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| The coolant temperature is less than 70 °C (less than 80 °C at very low ambient temperatures). |
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