Checking cooling output of air conditioner (front): Audi Q7

🧭 Before you start

Fits: Audi Q7 (4L, 2005–2015)

• Special tools named: VAS 5051

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• Measure ambient temperature (it must be over 15 °C).
• Depending on the version of the front operating and display unit, Climatronic control unit J255, "“Econ”" mode can be recognised from the fact that the lamp in the Econ button lights or the lamp in the AC button does not light.
• Operation of the air conditioner can also be seen, for example, from the fact that the refrigerant pipe on the low-pressure side (thick pipe) cools down.
• On vehicles fitted with an air conditioner of "“Basic”" type, use a thermometer to measure the temperature of the air flowing out of the dash panel vents.

📋 Procedure

1. Measure ambient temperature (it must be over 15 °C).
2. Close doors, bonnet, windows and sunroof.
3. Open the vents in the dash panel, the rear centre console and the "“B”" and "“C”" pillars (on vehicles with a rear air conditioner).
4. Open the dash panel vents (the vents in the rear centre console and the "“B”" pillars remain closed on vehicles with no rear air conditioner).
5. Switch on ignition.

6. Select "“Econ”" mode (on front operating and display unit, Climatronic control unit J255 or on MMI) Owner's Manual and "“Infotainment/MMI”" Operating Manual. [Note: Depending on the version of the front operating and display unit, Climatronic control unit J255, "“Econ”" mode can be recognised from the fact that the lamp in the Econ button lights or the lamp in the AC button does not light.]
7. Start engine.
8. Start Guided Fault Finding for the air conditioner front operating and display unit, Climatronic control unit J255"Guided Fault Finding" function of vehicle diagnostic, testing and information system VAS 5051.
9. In the "“Reading measured value block”" function select the display group with the following values and check the display "Guided Fault Finding" function of vehicle diagnostic, testing and information system VAS 5051. [Note: On the absolute pressure scale, 0 bar corresponds to an absolute vacuum. Normal ambient pressure thus corresponds to an absolute pressure of roughly 1 bar. On the scales of most pressure gauges, 0 bar corresponds to an absolute pressure of one bar (can be seen from -1 mark below 0).At present, the measured value block on this vehicle only indicates values as whole numbers. The display fluctuates between two values if the measured pressure is between the two.The pressure in the refrigerant circuit depends on the ambient temperature. Due to heat emitted by components (e.g. radiator fan) pressure displayed with warm engine is slightly higher than that indicated for the relevant ambient temperature.If the pressure displayed is lower than that given in the table, check the signal of the air conditioner high-pressure sender G65. If no fault is found at the air conditioner high-pressure sender G65, there is insufficient refrigerant in the refrigerant circuit. The vehicle is to be taken to a workshop equipped with the necessary tools where the work can be performed by appropriately qualified personnel Air conditioner with refrigerant R134a87General information on air conditioner (air conditioner with refrigerant R134a, general information on air conditioner).]
10. Switch on the compressor. To do so, select "“Auto”" mode on the front operating and display unit, Climatronic control unit J255 ("“deluxe”" type) or deactivate the "“Econ”" function ("“basic”" type).
11. Make "“Lo”" temperature setting for the driver's and front passenger's side or set the rotary temperature switch of the front operating and display unit, Climatronic control unit J255 to the "“cold”" stop (depending on air conditioner version).
12. Set the air outflow direction on the front operating and display unit, Climatronic control unit J255 to "“dash panel vents”".
13. Select function "“Read measured value block”"Guided Fault Finding function of vehicle diagnostic, testing and information system VAS 5051.
14. Check the various display zones on the display of the diagnosis tester: [Note: The air conditioner compressor regulating valve N280 is actuated by the front operating and display unit, Climatronic control unit J255 such that the temperature of the air downstream of the evaporator in the front air conditioning unit reaches the specified value (approx. 2 to 5 °C):After starting the vehicle, a value greater than 75 % (0.55 A) is displayed for N280 actuation depending on the measured temperature, engine speed and electrical system voltage.As soon as the temperature measured by the evaporator output temperature sender G263 approaches the specified value, N280 actuation is cancelled and the compressor output thus reduced.If the pressure measured by the high-pressure sender G65 and displayed does not change and if actuation of the compressor is OK, check whether the compressor is actually being driven (an overload protection is fitted between the compressor and the pulley / drive unit; if this has been tripped, the compressor is not driven). If no fault can be detected, there is a problem with the refrigerant circuit. The vehicle is to be taken to a workshop equipped with the necessary tools where the work can be performed by appropriately qualified personnel Air conditioner with refrigerant R134a87General information on air conditioner (air conditioner with refrigerant R134a, general information on air conditioner). There may be problems with compressor control. Inform the workshop of the problem encountered.Connectors to air conditioner compressor regulating valve N280 and electric engine mounting are identical. If the connectors are interchanged, no entry is made in the fault memory, but the evaporator may ice up as the compressor is constantly actuated by the engine control unit.]
15. Press the recirculated-air mode button on the front operating and display unit, Climatronic control unit J255 (symbol for "“recirculated-air mode”" in button lights).
16. Set engine speed to 2000 rpm (start of time measurement).
17. In "“Read measured value block”" function, select display group with measured value of the evaporator output temperature sender G263Guided Fault Finding function of vehicle diagnostic, testing and information system VAS 5051.
18. Compare the measured value displayed (for G263) to the values in the graph.
19. If the required values are not attained, check the measured value of the evaporator output temperature sender G263. To do so, compare the measured values displayed for G263, the front left chest vent temperature sensor G385 and the front right chest vent temperature sensor G386 for example (only possible with "“Deluxe”" version). With the "“ Basic”" version, use a thermometer to measure the temperature of the air flowing out of the dash panel vents. [Note: Operation of the air conditioner can also be seen, for example, from the fact that the refrigerant pipe on the low-pressure side (thick pipe) cools down.]
20. Compare the measured value displayed for G263 to the measured values for G385 and G386 ("“Deluxe”" version only). "Guided fault-finding" function of vehicle diagnostic, testing and information system VAS 5051 . [Note: On vehicles fitted with an air conditioner of "“Basic”" type, use a thermometer to measure the temperature of the air flowing out of the dash panel vents.] [Note: The air flowing from the evaporator to the vents is warmed slightly by the heat radiated by the heat exchanger in the air conditioning unit and by leakage air flowing past the temperature flaps through the heat exchanger.] [Note: If no fault is found at the evaporator output temperature sender G263, the front left chest vent temperature sensor G385 or the front right chest vent temperature sensor G386, perform the measures to be taken in the event of temperature increase downstream of the evaporator (check operation of temperature flaps and corresponding control motors).With the "“deluxe”" version, the temperature of the air flowing out of the "“centre”" dash panel vents can also be measured using a commercially available thermometer.Problems with differences in the temperature of the air flowing out of the vents in the same setting (in control mode), this could be caused by e.g. air in the heat exchanger or a temperature flap (temperature flap in air conditioning unit does not close or open fully or does not reach end position) and "Guided Fault Finding" function of vehicle diagnostic, testing and information system VAS 5051.]

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