Checking cooling output - vehicles with manually controlled air conditioner — AUDI

🧭 Before you start

• Renewed: sender

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• Measure ambient temperature: It must be over 15 °C.
• This illustration shows the position of rotary controls (1, 2, 3) and buttons (4, 5) on a vehicle with left-hand drive. On vehicles with right-hand drive, the position may be different.
• The operation of the air conditioner can be detected e.g. from the fact that the refrigerant pipe on the low-pressure side (thick pipe from internal heat exchanger to air conditioner compressor) cools down .

📋 Procedure

1. Measure ambient temperature: It must be over 15 °C.
2. Close doors, bonnet, windows, sunroof and rear lid.
3. Open all dash panel vents.
4. Start engine.
5. Make the following settings on the operating units for the air conditioning system: [Note: This illustration shows the position of rotary controls (1, 2, 3) and buttons (4, 5) on a vehicle with left-hand drive. On vehicles with right-hand drive, the position may be different.]

6. Switch off air conditioner compressor on Operating and display unit 3 for air conditioning system E776(2): Lamp in AC button (in rotary control (2)) not on.
7. Select the "“Read measured values”" function ("“Guided Fault Finding”" for the J255).
8. Read out activation of air conditioner compressor regulating valve N280.
9. Read measured value of pressure sender for refrigerant circuit G805. [Note: On the absolute pressure scale, 0 bar corresponds to an absolute vacuum. Normal ambient pressure thus corresponds to approx. 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 1 bar (can be seen from -1 mark below 0).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.]
10. Check signal of G805 ("“Guided Fault Finding”" for the J255).
11. The necessary work may only be performed by appropriately qualified personnel. If this is not possible on your premises, the vehicle must be taken to a workshop equipped with the necessary tools where this work can be performed by appropriately qualified personnel Air conditioner with refrigerant R134a 87. General notes on air conditioning systems. Inform the workshop of the problem detected.
12. Make the following settings on the operating units for the air conditioning system:
13. "“Read measured values”" ("“Guided Fault Finding”" for the J255).
14. Check display in display zones:
15. Check again whether the calculated current is actually flowing via the air conditioner compressor regulating valve N280 and the air conditioner compressor is actually being driven.
16. The necessary work may only be performed by appropriately qualified personnel. If this is not possible on your premises, the vehicle must be taken to a workshop equipped with the necessary tools where this work can be performed by appropriately qualified personnel Air conditioner with refrigerant R134a 87. General notes on air conditioning systems. Inform the workshop of the problem detected. [Note: N280 is activated by J255 so that the temperature of the air downstream of the evaporator reaches the specified value (approx. 2 to 6 ℃).After starting the vehicle, a value greater than 0.55 A (75 %) 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 .If no current is displayed in the measured values for the activation of the air conditioner compressor regulating valve N280 or if the current is too low, check the activation of N280 ("“Guided Fault Finding”" for the J255).]
17. Activate air recirculation mode using the fresh air and air recirculation mode button E781.
18. Set the engine speed to 2000 rpm (start of time measurement).
19. "“Read measured values”" ("“Guided Fault Finding”").
20. Compare the measured value displayed for the evaporator output temperature sender G263 to the values in the graph.
21. Use a thermometer to measure temperature of air emerging from dash panel vents (left and right).
22. Compare measured value to measured value displayed for evaporator output temperature sender G263.
23. Perform Fault Finding measures to be taken if readout does not match specification (see the separate procedure).
24. Check that G263 is correctly installed and perform electrical check for this sender ("“Guided Fault Finding”" for the J255). [Note: The operation of the air conditioner can be detected e.g. from the fact that the refrigerant pipe on the low-pressure side (thick pipe from internal heat exchanger to air conditioner compressor) cools down .]
25. Use a thermometer to measure temperature of air emerging from left (1) and right (2) dash panel vents.
26. Compare measured values on thermometer and for evaporator output temperature sender G263.
27. Check that evaporator output temperature sender G263 is installed correctly and check its wiring for any contact resistance; renew sender if defective ("“Guided Fault Finding”").
28. Check activation and operation of temperature flap. To do so, perform Fault Finding in the event of an increase in temperature downstream of the evaporator and ("“Guided Fault Finding”" for the J255).

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