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Adjusting CO2 content in exhaust gas of auxiliary heater > < Checking CO2 content in exhaust gas of auxiliary heater

A4 Mk2

Checking
Checking
   
–  Switch on the 4-component exhaust gas tester -V.A.G 1788- and insert the appropriate exhaust probe hose -B- in the auxiliary heater exhaust pipe -A-.
  Note
The hose -B- of the exhaust probe must not stop exhaust gas emerging from the exhaust pipe -A- during the test.
–  Switch on ignition.
–  Set maximum heat output on operating and display unit, Climatronic control unit -J255- of air conditioner/heater.
–  Restrict fresh-air blower speed by setting operating and display unit, Climatronic control unit -J255- to 5 bars (approx. 50 % of maximum fresh-air blower speed).
–  Switch on auxiliary heater by way of rotary knob/pushbutton in centre console or switches on windscreen wiper stalk → Chapter.
–  Switch off ignition.
–  Wait until auxiliary heater switches from starting to full load mode (approx. 3 minutes).
  Note
The instantaneous auxiliary heater operating status can be seen in the measured value block “Display group 006” → Chapter (Reading measured value block).
–  Wait at least 1 more minute after auxiliary heater has switched to full load operation.
–  Read measured value for CO2 (carbon dioxide) content in exhaust gas off CO2 measuring instrument (as of approx. 4 minutes after switch-on, auxiliary heater must be in full load operation).
  Note
  A82-0350
The hose -B- of the exhaust probe must not stop exhaust gas emerging from the exhaust pipe -A- during the test.
Specification:
t  For all vehicles (with petrol or diesel engine): 8.5 to 10.5 % by vol. CO2
  Note
t  If the measured value is in the lower range (less than 9%), problems may be encountered with auxiliary heater combustion under unfavourable usage conditions (e.g. high vehicle speed with auxiliary heater switched on). Set the CO2 content in the exhaust gas to a higher value → Chapter.
t  If the value displayed by the CO2 measuring instrument fluctuates slightly, form the mean from the highest and lowest measured value.
t  If the value displayed by the CO2 measuring instrument fluctuates considerably (more than approx. +/- 0.6% depending on measuring instrument), check the position of the measurement probe in the auxiliary heater exhaust pipe.
t  If the measured value is outside the permitted range:
t  Check the fresh-air intake hose and the auxiliary heater exhaust system for contamination or cross-sectional constriction and clean or replace these components if necessary.
t  Check the fuel delivery of the metering pump -V54- → Chapter.
t  If the CO2 content of the exhaust gas and the delivery of the metering pump -V54- are in the lower specified range, replace the metering pump -V54- → Chapter.
t  If the CO2 content of the exhaust gas is not OK although the fuel delivery is:
t  Check the fresh-air intake hose and the auxiliary heater exhaust system for contamination or cross-sectional constriction and clean or replace these components if necessary.
t  If no fault is found:
t  Check the combustion air blower -V6-.
t  Adjust the CO2 content of the exhaust gas → Chapter.
t  If the CO2 content of the exhaust gas cannot be adjusted, replace the combustion air blower -V6- → Chapter.
t  In the event of auxiliary heater starting problems despite correct fuel delivery and CO2 content in exhaust gas:
t  Check the glow plug for heater -Q9- → Chapter and → Chapter.
t  Remove any residue from the auxiliary heater combustion chamber (this is particularly important in the case of vehicles with diesel engine and when operating engine and thus auxiliary heater on vegetable-oil or rape-oil methylester fuel) → Chapter.
  A82-0350

Adjusting CO2 content in exhaust gas of auxiliary heater > < Checking CO2 content in exhaust gas of auxiliary heater