Refrigerant Circuit, Evacuating

WARNING: This page is about a different car, the 2022 Volkswagen ID.4 and 2021 Volkswagen ID.4. However, it is still accessible from the selected car via links, so may be relevant.

Special tools and workshop equipment required

Air Conditioning Service Unit R744 :VAS581009

As opposed to previous refrigerants, only larger leaks can be detected when evacuating R744.
If it is suspected that there is a leak in the refrigerant circuit, it must be located and repaired before charging the refrigerant circuit. Refer to LEAKS, FINDING .

The procedure must be performed as described in the operating instructions of the Air Conditioning Service Unit R744 :VAS581009 . Refer to Operating instructions of the A/C Service Station.
The quantity of refrigerant oil in the A/C Service Station is checked and if necessary corrected. Refer to the A/C Service Station Owner's Manual.
The refrigerant quantity in the A/C Service Station is checked and if necessary corrected. Refer to the A/C Service Station Owner's Manual.

The refrigerant circuit must be evacuated before it is filled with refrigerant (vacuum). Moisture is also extracted by this from the circuit.

Only larger leaks can be detected when evacuating the refrigerant circuit. Refer to LEAKS, FINDING .

Evacuating:

The refrigerant circuit is completely assembled.

-- Use the Vehicle Diagnostic Tester to perform the function "Refrigerant circuit, charging/evacuating/flushing".

The Vehicle Diagnostic Tester must not be disconnected from the vehicle during this process.
It is absolutely necessary to perform the "Refrigerant circuit, charging/evacuating/flushing" function with the Vehicle Diagnostic Tester so that all of the refrigerant circuit valves are opened. Only then can the entire circuit be evacuated, charged or flushed.

-- Deactivate drive ready mode and switch off all electrical equipment.

-- Connect the A/C Service Station to the power supply.

-- Start the A/C Service Station according to its operating instructions. Refer to the A/C Service Station Operating Instructions.

-- Remove the caps from the refrigerant circuit service connections (refer to the vehicle-specific refrigerant circuit). Refer to Refrigerant Circuit (vehicle-specific Service Information).

-- Check the refrigerant circuit service connections for debris and corrosion and if necessary clean.

Dirt or a rough surface on the service connections due to corrosion can cause seal damage, which can then cause premature failure of the quick-release couplings.

-- Connect the A/C Service Station to the refrigerant circuit. Refer to A/C SERVICE STATION ON REFRIGERANT CIRCUIT, CONNECTING .

-- Turn on the A/C Service Station, evacuate the refrigerant circuit, and perform the vacuum test.

NOTE:

The vacuum at the end of the evacuation process must be less than 5 mbar (0.07 psi) absolute pressure (the vacuum pump of the A/C Service Station runs). If during the evacuation process the refrigerant circuit pressure is not smaller than 5 mbar (0.07 psi), this may have various causes: For example, a leak in the refrigerant circuit or in the connection to the A/C Service Station, the time set for the evacuation process is too short, the vacuum pump for the A/C Service Station does not generate the required amount of vacuum, or the vacuum sensor on the A/C service station is not calibrated correctly. Refer to the A/C Service Station Owner's Manual.

With an ambient pressure of 980 mbar (14.21 psi), for example, an absolute pressure of 5 mbar (0.07 psi) equates to a vacuum of 975 mbar (14.14 psi).

At the end of the vacuum/pressure increase test, the refrigerant circuit pressure must not be higher than 60 mbar (0.87 psi) absolute pressure. If the refrigerant circuit pressure during the vacuum/pressure increase test becomes greater than 60 mbar (0.87 psi), the vacuum pump is switched on and the procedure starts over again from the beginning. Refer to the A/C Service Station Owner's Manual. If the procedure is repeated for a second time and the refrigerant circuit pressure still does not stay under 60 mbar (0.87 psi), this may have various causes. For example, a leak in the refrigerant circuit, a leak in the connection from the refrigerant circuit to the A/C Service Station or in the A/C Service Station itself, the time set for the evacuation process is too short, or the time set for the vacuum/pressure increase test is too long.

Depending on the version of the A/C Service Station, the refrigerant circuit pressure is immediately displayed; however, it is also possible that only when the vacuum pump is running is the current pressure shown. Refer to the A/C Service Station Owner's Manual. If the A/C Service Station only displays the ambient pressure, then the refrigerant circuit pressure display depends on the ambient pressure when activated (if the ambient pressure is 980 mbar (14.21 psi), a vacuum of 975 mbar (14.14 psi) equates to a residual pressure of 5 mbar (0.07 psi) absolute pressure).

If the refrigerant circuit was opened, a small amount of moisture may have entered the refrigerant circuit with the surrounding air. If this is the case, evacuate the refrigerant circuit for at least 40 minutes.

If refrigerant was extracted (to check the capacity) and the refrigerant circuit is only evacuated to fill it again (the refrigerant circuit was not opened and has no leaks), it may be sufficient to evacuate the refrigerant circuit for a lesser amount of time, and little to no time (for example, one minute) is needed for the vacuum/pressure increase test (no air and no moisture has entered the refrigerant circuit).

Depending on the quantity of refrigerant oil in the refrigerant circuit, the age and the mileage of the vehicle, the design of the refrigerant circuit etc., it is also possible that, on a leak-free refrigerant circuit, the specified absolute pressure in the refrigerant circuit rises over the specified 60 mbar (0.87 psi) during the vacuum test because of the refrigerant (and possibly even moisture) that has evaporated from the refrigerant oil. If this is the case, repeat the procedure again if necessary and/or adjust the pre-set times accordingly.

The pressure increase is within the permitted range and the system can be charged.

Depending on the version of the A/C Service Station the current refrigerant circuit pressure is constant or is displayed after switching off for example the "Evacuate" function. Refer to the A/C Service Station Owner's Manual.
Due to the high evacuation temperature, it may be that the refrigerant evaporating from the refrigerant oil is increasing the refrigerant circuit pressure to over 60 mbar (0.87 psi) (absolute pressure) during the vacuum test. This does not indicate a leak in the refrigerant circuit but depending on the version of the A/C Service Station can lead to a displayed malfunction. If necessary evacuate the refrigerant circuit again and monitor the vacuum indicator over a longer time, once the vacuum is maintained and it is ensured that there are no leaks in the refrigerant circuit, the system may be filled.

-- Charge the refrigerant circuit using the A/C Service Station. Refer to REFRIGERANT CIRCUIT, CHARGING .

If the vacuum is not maintained or if a sufficient vacuum cannot be generated, perform the following:

-- Evacuate the refrigerant circuit again with the A/C Service Station and perform the vacuum test.

The pressure increase is within the permitted range and the system can be charged.

-- Charge the refrigerant circuit using the A/C Service Station. Refer to REFRIGERANT CIRCUIT, CHARGING .

If there is a leak that allowed enough air to enter during evacuation that the A/C Service Station cannot generate a sufficient vacuum or that the vacuum is lost immediately after switching the A/C Service Station off:

-- Locate any leaks in the refrigerant circuit. Refer to LEAKS, FINDING .

If there is work to be performed on the vehicle after evacuating that does not require using the A/C Service Station

-- Disconnect the A/C Service Station from the refrigerant circuit and turn it off. Refer to A/C SERVICE STATION, SWITCHING OFF AND DISCONNECTING FROM REFRIGERANT CIRCUIT .

CAUTION:

Risk of damaging the A/C compressor by the refrigerant circuit vacuum.

- Never start the engine with vacuum in the refrigerant circuit.

-- Make sure that when charging the refrigerant circuit the engine cannot be started.

If after discharging and evacuating the refrigerant circuit cannot be refilled. Refer to REFRIGERANT CIRCUIT, CHARGING .