Checking - vehicles without high-voltage system: Audi A6/A7 C7

🧭 Before you start

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

Don't miss

• Measure ambient temperature (it must be over 15 °C).
• Various measured values can be selected for the following test and displayed in a table in "“Guided Fault Finding”" mode.
• Pressing the SYNC button on J255 ("“Deluxe”" version only) stores the settings for the front driver's side at the front passenger's side as well and if applicable also at E265.

📋 Procedure

1. Measure ambient temperature (it must be over 15 °C).
2. Close doors, bonnet, windows, sun roof and rear lid.
3. Open all the dash panel vents and the vent in the rear centre console.
4. On an air conditioner of the "“deluxe”" type, open the vents in the B-pillars.
5. Start engine.

6. Switch off the air conditioner compressor ("“Econ”" mode set on operating unit (Climatronic control unit J255) lamp in AC button not lit).
7. Start air conditioner Guided Fault Finding (on operating unit, Climatronic control unit J255 in "“Guided Fault Finding”" mode.
8. Select and read out the measured values for actuation of the air conditioner compressor and the pressure in the refrigerant circuit in the "“Read measured values”" function in "“Guided Fault Finding”" mode. [Note: Various measured values can be selected for the following test and displayed in a table in "“Guided Fault Finding”" mode.] [Note: On the absolute pressure scale, 0 bar corresponds to an absolute vacuum. Normal ambient pressure thus corresponds to roughly 1 bar absolute and 0 bar gauge pressure. On the scales of most pressure gauges, 0 bar gauge pressure corresponds to an absolute pressure of one bar (can be seen from -1 mark below 0).Depending on the version of J255, only whole numbers may be indicated as measured values. 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 the radiation of heat by components (e.g. radiator), the pressure displayed when the engine is warm is slightly higher than that given for the corresponding ambient temperature.If the displayed pressure is lower than that given in the table: Check the signal of the refrigerant pressure and temperature sender G395 in "“Guided Fault Finding”" mode. If no fault is found at the G395, there is not enough refrigerant in the circuit. The vehicle must be taken to a workshop which is equipped with the necessary tools and at which the work can be performed by appropriately qualified personnel Air conditioner with refrigerant R134a87Refrigerant circuit (Working with the air conditioner service station).]
9. Switch on air conditioner compressor by selecting "“Auto”" mode on operating unit (Climatronic control unit J255 and also on E265 if fitted); lamps in AUTO button(s) and AC button will light up. [Note: Pressing the SYNC button on J255 ("“Deluxe”" version only) stores the settings for the front driver's side at the front passenger's side as well and if applicable also at E265.]
10. Set air conditioner to "“cold”" temperature setting (for driver's and passenger's side) using rotary control on J255.
11. On vehicles with rear Climatronic operating and display unit E265, also set rear temperature to "“cold”" (for left and right side).
12. By way of the rotary controls on J255, set the air delivery to "“dash panel vents”" (for driver's and front passenger's side).
13. On vehicles with E265, set the air delivery by way of the rotary controls on E265 to the vents in the rear centre console. [Note: The lamp in the AUTO button(s) 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.).]
14. In the "“Read measured values”" function, read out the actual current with which the air conditioner compressor regulating valve N280 is actuated (an actual current greater than 0.3 A is displayed, the air conditioner compressor is switched on) in "“Guided Fault Finding”" mode. [Note: The specified current for actuating the air conditioner compressor regulating valve N280 is calculated by J255. The request is transmitted via the data bus to the onboard supply control unit J519, J519 actuates N280 and provides feedback on the actual current in "“Guided Fault Finding”" mode.If no or insufficient current is displayed as measured value, check activation of N280in "“Guided Fault Finding”" mode.N280 is actuated by J255 via J519. Actuation of N280 is also displayed as measured value in J519 in "“Guided Fault Finding”" mode.The actual current flowing via N280 is measured by J519 and transmitted by way of the data bus to J255 in "“Guided Fault Finding”" mode.]
15. In the "“Read measured values”" function, read out the pressure in the refrigerant circuit measured by the refrigerant pressure and temperature sender G395. The pressure displayed increases to above the value with the air conditioner compressor switched off in "“Guided Fault Finding”" mode. [Note: If the pressure displayed as measured value does not change and actuation of the air conditioner compressor is OK in "“Guided Fault Finding”" mode, check again whether the air conditioner compressor is actually being driven and the air conditioner compressor regulating valve N280 actuated. There is a fault in the refrigerant circuit if the air conditioner compressor is being driven and N280 actuated. Take the vehicle to a workshop which is equipped with the necessary tools and at which the work can be performed by appropriately qualified personnel (there may be problems with control of air conditioner compressor) Air conditioner with refrigerant R134a87Refrigerant circuit. Inform the workshop of the problem detected.N280 is actuated by J255 (via J519) such that the temperature of the air downstream of the evaporator reaches the specified value (approx. 2 to 5 °C).After starting the vehicle, a value greater than 0.55 A is displayed for actuation of N280 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, activation is cancelled and the compressor output thus reduced.Under certain operating conditions, residual moisture in the refrigerant circuit may lead to the formation of ice at N280 (and at the expansion valve). Such ice formation impedes the control of the air conditioner compressor. The evaporator is cooled down too much and ices up. An iced-up evaporator may cause various problems .]
16. Press the air recirculation mode button on the operating unit, Climatronic control unit J255 (the symbol for "“air recirculation mode”" in the air recirculation button lights).
17. Set the engine speed to 2000 rpm (start of time measurement).
18. In the "“Read measured values”" function, read out the measured value of the evaporator output temperature sender G263 in "“Guided Fault Finding”" mode.
19. Use thermometer to measure temperature of air from vent in rear centre console.
20. Compare measured value displayed (for G263) to values in graph. [Note: If the required values at the front are not attained, check the measured value of G263. To do so, compare the measured value displayed for G263 to the measured values of the left vent temperature sender G150 and the right vent temperature sender G151.If the measured value for G263 only differs slightly from the measured value for G150 / G151, Perform Fault Finding if readout does not match specification .If the measured value for G263 is greater than the measured value for G150 and/or G151, check for proper installation of G263 and perform the electrical checks for this sender "“Guided Fault Finding”" functionIf the measured temperatures from the rear centre console vents are more than 1 °C lower than the measured value for G263, check the temperature sensors used for measurement (the design of the air conditioner is such that the temperature at the rear cannot be lower than at the front).One way to check whether the air conditioner is working is by feeling the refrigerant lines: the "“low-pressure side”" refrigerant line (thick line between internal heat exchanger and air conditioner compressor) cools down and the "“high-pressure side”" refrigerant line (thin line between condenser and internal heat exchanger) becomes warm .]

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