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| If voltage is not applied to the heater coolant shut-off valve -N279- (large coolant circuit), the coolant can flow from connection -A- (from the heat exchanger in the air conditioner unit) to connection -B- (to the engine). |
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| There are different versions of -N279- (with 3 or 4 connections for coolant hoses). On the version with 4 connections, one connection is sealed with a cap. |
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| Depending on the installation position of -N279-, the cap shown may also be fitted at connection -C-. |
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| If voltage is applied to the heater coolant shut-off valve -N279- (small coolant circuit), the coolant can flow from connection -A- (from the heat exchanger in the air conditioner unit) to connection -C- (to the circulation pump -V55-). |
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| Depending on the model and the engine, the vehicle may additionally be fitted with a non-return valve in the coolant circuit. A certain amount of coolant then flows back to the engine via this non-return valve in the small circuit if the heater coolant shut-off valve -N279- is being actuated → Chapter. |
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| Depending on the vehicle model, the engine fitted, the coolant temperature and the setting on the operating and display unit, Climatronic control unit -J255-, -N279- may also be actuated by the supplementary heater control unit -J364- with the auxiliary heater switched off. In this case, actuation is in response to a request from the operating and display unit, Climatronic control unit -J255- via the data bus → Air conditioning; Rep. Gr.87. |
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| The -N279- currently fitted on the Audi Q5 (with 3 connections for coolant hoses) is only to be actuated up to a certain engine speed (currently up to approx. 1200 rpm). At higher engine speeds, -N279- no longer opens on completion of actuation on account of the resultant higher delivery of the engine coolant pump and the heated engine coolant does not flow through the heat exchanger in the air conditioner unit. Attention is therefore to be paid to the correct version, encoding and adaption of the auxiliary heater → Vehicle diagnostic, testing and information systemVAS 5051/, “Guided fault-finding function”. |
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