Note | If the coolant circuit is not completely bled after filling, air may accumulate in the heating system heat exchanger and thus reduce the heat output. In addition, noise may occur or complaints may be received about differences in the temperature of the air from the driver's and front passenger's vents. |
| Remedy in the event of poor heat output or noise from the coolant circuit: |
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| Perform a lengthy test drive at high engine speed (at least 10 minutes, engine speed above 2500 rpm). In doing so, select a low gear to prevent excessive vehicle speed. |
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| In the event of complaints about poor heat output at certain engine speeds, check incorporation of the heating system heat exchanger into the coolant circuit. If the two coolant hoses (supply and return) from the engine have been interchanged, coolant will flow in the wrong direction through the heat exchanger. → Engine, mechanics; Rep. gr.19 |
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| On vehicles with auxiliary/supplementary heater, check actuation of the circulation pump -V55- of the auxiliary heater as well as incorporation of the auxiliary heater into the coolant circuit. |
| Requirements for attaining maximum heat output: |
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| All air ducts, covers and seals OK and properly installed. |
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| Air throughput of dust and pollen filter not impaired by dirt, checking → Chapter |
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| Bowden cable and temperature flap actuating levers Ok. |
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| Foam seal at heating system heat exchanger OK → Chapter. |
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| On vehicles with petrol direct injection engine „FSI“, actuation of engine control unit by heater control unit -J65- OK → Chapter |
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| All air ducts, covers and seals OK and properly installed |
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| Air flow through dust and pollen filter not impaired by dirt |
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| Vehicle not exposed to sunlight. |
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| Close the doors, windows and sun roof. |
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| Open all dash panel vents. |
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| Measure the ambient temperature (temperature in the workshop). |
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| Set the rotary temperature control to the „cold“ stop. |
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| Set the air outflow direction to „dash panel vents“ by way of the rotary air distribution control. |
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| Set speed „4“ at the fresh air blower rotary control. |
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| Use a thermometer to measure the temperature of the air emerging from the left and right dash panel vents. |
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| The heater operates in fresh air mode, the indicator lamp in the air recirculation button -D- does not light. |
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| The fresh air blower runs at maximum speed. |
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| The temperature of the air emerging from the left and right dash panel vents is max. 15 °C higher than the previously measured ambient temperature. |
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| The difference in the temperature of the air emerging from the dash panel vents on the left and right is less than 8 °C. |
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| Set the highest possible temperature (rotary temperature control on „warm“ stop). |
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| Use a thermometer to measure the temperature of the air emerging from the left and right dash panel vents. |
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| The temperature of the air emerging from the dash panel vents on the left and right increases to a value above 55 °C (at an engine temperature of approx. 90 °C, depending on the instantaneous engine temperature). |
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| The difference in the temperature of the air emerging from the dash panel vents on the left and right is less than 8 °C. |
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| Set the lowest possible temperature (rotary temperature control on „cold“ stop). |
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| Use a thermometer to measure the temperature of the air emerging from the left and right dash panel vents. |
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| Within 5 minutes the temperature drops to a value max. 15 °C higher than the previously measured ambient temperature. |
| Check the following if the readout does not match the specifications: |
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| If the required heat output is not attained |
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| Bowden cable for temperature adjustment and actuation of temperature flaps → Chapter |
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| The foam seal at the heating system heat exchanger → Chapter. |
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| Operation of the temperature flaps in the air distribution housing → Chapter. |
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| If the air emerging from the vents is too warm in the „cold“ setting |
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| Bowden cable for temperature adjustment and actuation of temperature flaps → Chapter |
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| Operation of the temperature flaps in the air distribution housing → Chapter. |
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| Plenum chamber cover and seal between engine compartment and plenum chamber |
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