Refrigerant Circuit, Discharging

Special tools and workshop equipment required 

• Air Conditioning Service Unit R744 :VAS581009 

-- 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.

Refrigerant, Draining

• Work procedure may vary depending on the type of tools selected (the tool-specific operating instructions should therefore be followed). Refer to the A/C Service Station Owner's Manual.
• The refrigerant circuit must be discharged if parts of the refrigerant circuit are to be removed, if there is any doubt about the amount of refrigerant in the circuit, or if it is required by the safety precautions.
• All the important operating instructions for working with the Air Conditioning Service Unit R744 :VAS581009  can be found in the operating instructions of the A/C Service Station. Refer to Operating Instructions A/C Service Station.

Discharging:

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

-- Start the A/C Service Station according to the corresponding 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 .

-- Discharge the refrigerant circuit using the A/C Service Station according to the operating instructions.

Should work be performed on the vehicle after discharging which 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 .

-- Open the refrigerant circuit at a connection location.

• For all following procedures immediately seal all the open lines and connections with clean plugs from the Engine Bung Set :VAS6122  .

-- Perform the specified procedures on the refrigerant circuit.

Should the refrigerant circuit be evacuated and recharged after the discharging. Refer to REFRIGERANT CIRCUIT, EVACUATING .

• If the refrigerant oil is also drained from the refrigerant circuit with the refrigerant, the same amount of fresh refrigerant oil must be added back to the circuit when charging. Refer to the Parts Information.

• Depending on the version of the A/C Service Station, it can generate a vacuum in the refrigerant circuit when draining the refrigerant (residual pressure less than approximately 300 mbar (4.35 psi)).
• 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 on a vehicle with a refrigerant circuit with an expansion valve or check valve, then it may take some time until the pressure on the high-pressure side decreases (the check valve prevents the refrigerant from flowing out of the reservoir and back to the high-pressure side, or the expansion valve is cold and the pressure on the low-pressure side quickly increases after it is turned off, the expansion valve closes and the refrigerant can only 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.