Checking heating output and activation of temperature flaps - "“basic”" version — AUDI

🧭 Before you start

Fits: Audi A6/A7 C7 (4G, 2011–2018); platform code 4X

• Renewed: defective sender

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• On account of the design of the air conditioning unit and the air routing in the vehicle there is always a certain increase in the temperature of the air as it is conveyed from the evaporator to the vents.
• Depending on the G538 and J255 setting, the temperature of the air from the rear centre console vent is only regulated as tendentially "“cooler”" or "“warmer”" than that from the dash panel vents.
• After setting the temperature for the driver's side to "“cold”" and for the passenger's side to "“warm”", this test can be repeated with the opposite measured values.

📋 Procedure

1. Close bonnet.
2. Close doors, bonnet, windows, sun roof and rear lid.
3. Open all the dash panel vents and the vents in the rear centre console.
4. Start engine. [Note: The potentiometer for rear temperature selection G538 is only fitted in the rear centre console in a certain country-specific version.The temperature flaps for the rear vents are actuated (by the rear temperature flap control motor V137) by way of a characteristic curve stored in the operating unit, Climatronic control unit J255. If there is a considerable difference between the settings for the left and right side in J255 and / or the setting for the potentiometer for rear temperature selection G538, the temperature flaps for the rear vents are no longer moved to the end stops. The temperature flaps for the temperature of the air from the rear vents are then only actuated such that this air tends to be slightly warmer or colder than for the front vents, depending on the setting on G538.] [Note: The lamp in the AUTO button goes out when the air outflow direction and/or the fresh air blower speed is/are altered manually.The maximum possible fresh air blower speed depends on several factors (electrical system voltage etc.).Dash panel vents and vents in rear centre console open.]
5. Select air conditioner "“Read measured values”" function on J255 in "“Guided Fault Finding”" mode.

6. Run the air conditioner for several minutes at maximum cooling output.
7. Compare the measured value of G263 to the measured values of G150, G151, G261 and G262. [Note: On account of the design of the air conditioning unit and the air routing in the vehicle there is always a certain increase in the temperature of the air as it is conveyed from the evaporator to the vents.]
8. If the required front temperature sensor values are not obtained, perform the measures to be taken in the event of an increase in temperature downstream of the evaporator . [Note: If the measured value for one or two temperature sensors differs from the measured values of the other temperature sensors, check this temperature sensor and the control motor which actuates the temperature flap upstream of this temperature sensor in "“Guided Fault Finding”" mode.]
9. If the required values are not obtained for the air from the rear centre console vent, take the appropriate action Measures to be taken if cooling output of front air conditioner is OK, but the required values are not attained at the rear "Basic" version.
10. Read off the measured values displayed for the various temperature sensors G150, G151, G261 and G262. [Note: On vehicles with no coolant circulation pump V50/ circulation pump V55, it may be necessary to increase the engine speed slightly to approx. 1400 rpm to obtain the required coolant throughput through the heating system heat exchanger in the air distribution housing.]
11. Use the rotary switch (5) on the operating unit, Climatronic control unit J255 to set the temperature for the passenger side (front and rear) to "“cold”".
12. Leave the temperature setting for the driver side (front and rear) on "“warm”".
13. Select air conditioner "“Read measured values”" function on J255 in "“Guided Fault Finding”" mode.
14. Run the air conditioner for several minutes in this setting.
15. Compare the measured value of the evaporator output temperature sender G263 to the measured values of G150, G151, G261 and G262. [Note: If the temperature setting for one side (driver's or passenger's side) is "“warm”", the specified output temperature at the evaporator is regulated by the operating unit, Climatronic control unit J255 to a higher value (up to approx. 10 °C).The temperature of the air emerging from the rear vents is regulated by the operating unit, Climatronic control unit J255.]
16. Set the temperature for the right side on J255 to "“warm”" and wait several minutes.
17. Measure the temperature of the air from the rear centre console vent.
18. On G538 set the knurled wheel (1) to "“cold”".
19. On G538 set the knurled wheel to "“warm”". [Note: Depending on the G538 and J255 setting, the temperature of the air from the rear centre console vent is only regulated as tendentially "“cooler”" or "“warmer”" than that from the dash panel vents.]
20. Check operation of G538 in "“Guided Fault Finding”" mode for J255. [Note: After setting the temperature for the driver's side to "“cold”" and for the passenger's side to "“warm”", this test can be repeated with the opposite measured values.]
21. Pinch off the two coolant hoses to the heat exchanger of the front air conditioning unit using hose clamps 3093 for example .
22. Repeat checking of the heat output and actuation of the temperature flaps with "“cold”" set on the operating unit .
23. Compare the measured value of the evaporator output temperature sender G263 to the measured values of G150, G151, G261 and G262.
24. Do the measured values of the temperature sensors coincide with the coolant hoses pinched off and are the required values attained?
25. Detach the hose clamps 3093 from the two coolant hoses.
26. Check the sender supplying the deviating measured value for correct installation, as well as the electrical connections for contact resistance in "“Guided Fault Finding”" mode .
27. Check the actuation and operation of the temperature flap control motor V158 / V159 and the rear temperature flap control motor V137 as well as actuation of the corresponding temperature flap Air intake and air outlet openings.
28. Eliminate cause of incorrect measured value; renew defective sender if necessary.
29. Check operation of the temperature flap producing the temperature increase in the "“cold”" setting Exploded view - flaps and partitions in air distribution housing.
30. Check the heat output and actuation of the temperature flaps again .
31. Eliminate the cause of the malfunction in "“Guided Fault Finding”" mode and
32. Check the heat output and actuation of the temperature flaps again .

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