Refrigerant Circuit, Discharging With A/C Service Station
- Work procedure may vary depending on the type of tools selected (the tool-specific operating instructions should therefore be followed).
- The refrigerant circuit is to be discharged if parts of the refrigerant circuit are to be removed, if there is any doubt about the quantity of refrigerant in the circuit or if the safety precautions so require.
- All the necessary usage information for working with the refrigerant A/C service station can be found in the A/C service station operating instructions.
Discharging:
-- On vehicles with a high-voltage system, switch off (deactivate) the "auxiliary climate control" function. Refer to the Owner's Manual and Infotainment/MMI Operating Manual.
-- Switch off the ignition.
-- Connect the A/C service station to the vehicle service connections according to the operating instructions and start the A/C service station. Refer to vehicle-specific refrigerant circuit and Refrigerant Circuit .
Also for vehicles with electrically operated valves in the refrigerant circuit that cannot be opened without current (for example the Audi Q7 e-tron):
For vehicles with a high-voltage system and additional A/C system functions ("heat pump operation" or "cooling the high-voltage battery"), valves may be installed in the refrigerant circuit that cannot be opened without current. These valves are opened and closed via stepper motors, for example, and are no longer activated after switching off the ignition. To completely discharge, correctly evacuate and charge the refrigerant circuit, no sections may be closed. Therefore these valves must be opened before performing this work. Refer to Refrigerant Circuit and use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
-- Open the electrically activated valves (not open without current) using the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
-- Discharge the refrigerant circuit using the A/C service station according to the operating instructions.
There is a risk of damaging the A/C compressor if the refrigerant circuit is empty.
Do not start the engine if the refrigerant circuit is empty.
- Depending on the version of the A/C service station, the refrigerant circuit pressure may be less than 1 bar absolute pressure after it has been discharged.
- Depending on the version of the A/C compressor, it may be damaged if it is operated when there is low refrigerant circuit pressure.
- Do not start the engine while the refrigerant circuit pressure is less than the ambient pressure.
There is a risk of freezing.
Refrigerant may leak out if the refrigerant circuit is not discharged.
Refrigerant must be extracted before opening the refrigerant circuit. If the refrigerant circuit is not opened within 10 minutes of extraction, pressure may form in refrigerant circuit due to evaporation. Extract the refrigerant again.
There is a possibility of refrigerant oil being extracted from the refrigerant circuit together with the refrigerant. To ensure A/C compressor lubrication, the refrigerant oil in the circuit must be topped up with fresh oil. Refer to REFRIGERANT R134A CAPACITIES, REFRIGERANT OIL AND APPROVED REFRIGERANT OILS .
For vehicles with an A/C compressor with no A/C clutch (with an A/C Compressor Regulator Valve -N280-), the engine should not be run for longer than absolutely necessary with the refrigerant circuit empty. Avoid higher engine speeds (A/C compressor always in operation as well).
For vehicles with an A/C compressor with no A/C clutch, the engine may only be started following complete assembly of the refrigerant circuit (avoid high engine speeds).
Depending on the A/C compressor version, there may be a valve installed on the high pressure side of the A/C compressor, which prevents the liquid refrigerant from flowing back into the A/C compressor once the A/C system is turned off. If an A/C compressor with this valve is installed in a vehicle with a refrigerant circuit having an expansion valve, then it may take some time until the pressure in the high pressure side decreases (the expansion valve is cold and the pressure in the low pressure side quickly increases after it is turned off, the expansion valve closes and the refrigerant can flow slowly to the low pressure side). If the A/C compressor is switched on (or the refrigerant circuit is evacuated on the low pressure side), the pressure on the low pressure side goes down, the expansion valve opens and the refrigerant can flow to the low pressure side.
Depending on the version of the A/C service station, the previous operating condition and the ambient temperatures, etc., the amount displayed by the A/C service station for the extracted refrigerant R134a can vary from the actual extracted amount. The amount displayed by the A/C service station for the extracted refrigerant is therefore only a reference point for the amount of refrigerant actually extracted from the refrigerant circuit. Also pay attention to the A/C service station operating instructions and technical product description.
Should work be performed on the vehicle after discharging that does not require using the A/C service station
-- Disconnect the A/C service station from the refrigerant circuit and turn it off.
Should the refrigerant circuit be evacuated and recharged after the discharging. Refer to REFRIGERANT CIRCUIT, CHARGING WITH A/C SERVICE STATION .