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Home >> Audi >> 2012 >> Q7 3.0 TDI >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Heating, Ventilation & Air Conditioning >> 87 Air Conditioning >> Diagnosis And Testing >> Front A/C System Performance, Checking >> Determining Malfunction During Temperature Increase Downstream Of Front Evaporator

Determining Malfunction During Temperature Increase Downstream Of Front Evaporator

-- Clamp off both coolant hoses from engine to heating & A/C unit (for example, using hose clamp up to 25 mm dia.3094 in left front wheel housing), refer to INCORPORATION OF FRONT HVAC SYSTEM INTO COOLING CIRCUIT .

-- Repeat cooling performance test, refer to TEST REQUIREMENTS .

  • The measured value from the left front upper body vent temperature sensor and from the right front upper body vent temperature sensor (or the temperature of the air coming out of the vents in the instrument panel measured with a thermometer) differs less than 5 °C (41 °F) from the measured value from the Evaporator Vent Temperature Sensor -G263- using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding"  .
↓ Yes ↓ ↓ No ↓
-- Remove hose clamps using hose clamps up to 25 mm dia.3094 at both coolant hoses.↓ -- Check sensor which measuring value deviates for correct installation and electrical connection for contact resistance. ↓
-- Check activation of Left Temperature Door Motor -V158- and of Right Temperature Door Motor -V159-.
  • On vehicles with Basic version A/C system, only the measured value of evaporator vent temperature sensor can be checked.
  • Is the activation of Left Temperature Door Motor and of Right Temperature Door Motor OK?
 ↓ -- Eliminate cause of incorrect measured value, replace defective sender.
↓ No ↓ Yes    
↓ ↓    
-- Repair cause of malfunction, refer to Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding"  function. -- Check operation of Left Temperature Door Motor, refer to RETAINING PLATE WITH LEFT FOOTWELL DOOR MOTOR -V108- AND LEFT TEMPERATURE DOOR MOTOR -V158-  and of Right Temperature Door Motor, refer to RETAINING PLATE WITH CONTROL MOTORS -V158- / -V159- AND -V109- / -V108- .↓
Refer to the appropriate Wiring Diagram ↓ -- Is the function of Left Temperature door Motor and of Right Temperature door Motor and door operation OK?
-- Repeat cooling performance test, refer to TEST REQUIREMENTS . ↓ Yes ↓ -- Check function of respective temperature door in heating & A/C unit for example, with control motor removed.↓ ↓ No ↓ -- Repair the door actuation mechanism. ↓
  -- Repeat cooling performance test, refer to TEST REQUIREMENTS .
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