| Checking heat output and actuation of temperature flaps (air conditioner of „Basic“ type) |
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| Close the doors, windows, sun roof and rear lid. |
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| Open all dash panel vents. |
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| Switch on the ignition and activate READY, the engine starts automatically if required (on vehicles with a high-voltage system). |
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| Start the engine (not on vehicles with a high-voltage system) |
| Make the following settings on the air conditioner operating and display unit, Climatronic control unit -J255-: |
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| „Auto“ mode (lamp in AUTO button lights). |
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| „Cold“ temperature setting (display „LO“ on Multi Media Interface display) |
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| Air conditioner compressor switched on (lamp in AC button lights). |
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| „Maximum speed“ pre-selected for fresh air blower (speed „10“ or higher indicated in Multi Media Interface display). |
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| Use the rotary control to set the air outflow direction at the air conditioner operating and display unit to „footwell vents“ and „dash panel vents“ (indicated on display of Multi Media Interface). |
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| The lamp in the AUTO button goes out when the air outflow direction and/or the fresh air blower speed is/are altered manually. |
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| The maximum possible fresh air blower speed depends on various ambient influences (coolant temperature, vehicle electrical system voltage etc.). |
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| Allow the air conditioner to run for several minutes at maximum cooling output (air conditioner compressor switched on, lamp in AC button lights). |
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| Compare the measured value displayed for the evaporator output temperature sender -G263- to the measured values for the centre vent temperature sender -G191- and the footwell vent temperature sender -G192-. |
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| After 5 minutes, the measured values for -G191- and -G192- must not be more than 5 °C higher than that for -G263-. |
| If the required values are not obtained, perform the measures to be taken in the event of an increase in temperature downstream of the evaporator → Anchor. |
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| Use a commercially available thermometer to measure the temperature of the air emerging from the dash panel vents (left, right and centre) and the front and rear (left and right) footwell vents and compare the measured values to those displayed for -G191- and -G192-. |
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| The values measured with the thermometer must not be more than 5 °C lower or higher than the measured values displayed for -G191- and -G192-. |
| If the required values are not obtained, perform the measures to be taken in the event of an increase in temperature downstream of the evaporator → Anchor. |
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| Use the rotary control on the air conditioner operating and display unit, Climatronic control unit -J255- to select the „warm“ temperature setting (display „Hi“ on Multi Media Interface display). |
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| Use a commercially available thermometer to measure the temperature of the air emerging from the dash panel vents (left, right and centre) and the front and rear (left and right) footwell vents and compare the measured values to those displayed for -G191- and -G192-. |
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| In the display zones the measured values displayed for -G191- and -G192- increase to above 52 °C (depending on the instantaneous engine temperature). |
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| After 5 minutes, the readings (temperature of air emerging from vents) must not be more than 5 °C lower or higher than the measured values displayed for -G191- and -G192-. |
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| Depending on the engine (e.g. 8-cyl. engine), it may be necessary to increase the engine speed to between 1200 and 1500 rpm to attain the required temperature. At idle, the heat output of the engine or the volume of coolant conveyed through the heat exchanger is not sufficient with all engines to supply the heat exchanger with the heat energy required (e.g. on an 8-cyl.. engine with an idling speed of approx. 650 rpm). |
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| In the „warm“ temperature setting, the specified outflow temperature at the evaporator is regulated by the air conditioner operating and display unit, Climatronic control unit -J255- to approx. 10 °C. |
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| On vehicles with a high-voltage system, reduce the speed of the fresh air blower -V2- if applicable. With the engine stopped and maximum fresh air blower speed set, the delivery of the coolant circulation pump -V50- may not always be sufficient to attain the required heat output. |
| Check the following if the readout does not match the specifications: |
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| Repeat the heat output test at an engine speed of approx. 1500 to 2000 rpm (with a lower fresh air blower speed on vehicles with a high-voltage system). If the required heat output is attained at this engine speed (fresh air blower speed), the fault is not in the air conditioning unit, but rather in the coolant circuit (incorporation of air conditioner into coolant circuit, engine coolant pump delivery, flow of coolant through heat exchanger in air conditioning unit etc. → Chapter and → Engine, mechanics; Rep. gr.19). |
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| Foam seal at heat exchanger for heater of air conditioning unit → Chapter |
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| Proper operation of the engine coolant pump (if the coolant pump is defective, the amount of coolant flowing through the heating system heat exchanger in the air conditioning unit may not be sufficient) → Engine, mechanics; Rep. gr.19 |
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| The coolant circulation pump -V50- is not fitted on all vehicles (depending on model, engine and production period). On vehicles fitted with the optional extra, the circulation pump -V55- assumes the function of -V50-. The circulation pump -V55- is also actuated, depending on the vehicle model and the adaption of the supplementary heater control unit -J364-, by -J364- in response to a request from the air conditioner operating and display unit, Climatronic control unit -J255- at low engine speed to assist the engine coolant pump → "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051. |
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| On vehicles with a start-stop system and vehicles with a high-voltage system, the flow of coolant through the heating system heat exchanger in the air conditioning unit is maintained with the engine stopped by the coolant circulation pump -V50-. |
| Measures to be taken in the event of temperature increase downstream of evaporator |
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