| Note on vehicles with auxiliary heater (poor heat output) |
| In the event of problems with poor or inadequate heat output at low engine speeds on vehicles with auxiliary heater fitted as optional extra, check actuation of the auxiliary heater circulation pump -V55- by the auxiliary heater control unit -J364-. |
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| Actuation of the circulation pump -V55- increases the flow of coolant through the air conditioner heat exchanger at low engine speeds and thus improves heat output → Auxiliary heating; Rep. Gr.01. |
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| The auxiliary heater control unit -J364- switches on the circulation pump -V55- if it receives the following information via the convenience data bus system: |
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| Ignition switched on and engine running |
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| Ambient temperature less than 20 °C |
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| Engine speed less than 2000 rpm |
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| Operating and display unit, Climatronic control unit -J255- switched on (OFF button not pressed) |
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| At least one of the two temperature flaps not on “cold” stop |
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| The circulation pump -V55- is switched on as soon as all activation conditions are fulfilled. To stop the circulation pump being constantly switched off and on, it remains activated for at least 30 s even if - for example in the event of rapid changes in vehicle speed - a request is only applied for several seconds (e.g. on accelerating after standing at traffic lights). |
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| Vehicles with auxiliary heater and petrol engine with an operating and display unit, Climatronic control unit -J255- with hardware/software version as of “XX15” (index “H” onwards) are not to be fitted with an auxiliary heater control unit -J364- with hardware/software version “XX 09”. This combination can lead to problems with actuation of the circulation pump -V55- with the engine running. This problem no longer occurs with the auxiliary heater control unit -J364- as of hardware/software version “XX 10”. |
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