Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Refrigerant Circuit, Flushing With Compressed Air And Nitrogen
- Nitrogen can leak uncontrolled from the cylinder.
- Make exclusive use of pressure reducers for nitrogen cylinders (maximum work pressure 15 bar).
- Use appropriate emissions extraction units to draw off gas mixture escaping from components.
- In order to be able to force moisture and other contaminants out of refrigerant circuit, compressed air and nitrogen (to force moisture out of refrigerant circuit) are to be used.
- For the most part, blowing through the refrigerant circuit with compressed air and nitrogen requires significantly more work than flushing with refrigerant R134a. As flushing with refrigerant R134a cleans the components more efficiently, always flush in case of a complaint (blowing through should only be used for certain complaints and individual components).
Only individual components should be flushed if
- There is no possibility of flushing the refrigerant circuit with refrigerant R134a.
- Dirt or other contaminants are located in individual components of the circuit.
- Vacuum reading is not maintained on evacuating a leak-free refrigerant circuit (pressure build-up due to moisture in refrigerant circuit).
- Refrigerant circuit has been left open for longer than normal (for example following an accident).
- Pressure and temperature measurements in the refrigerant circuit indicate the likelihood of moisture.
- Stipulated by the vehicle-specific repair information. Refer to [For engine(s) BGP, BPY, BGQ, CBTA, CBUA, CCTA, CBFA] Removal and Installation following replacement of certain components.
Blowing compressed air and nitrogen through the refrigerant circuit does not achieve the level of cleanliness as flushing with refrigerant R134a. Flushing with refrigerant R134a loosens the refrigerant oil and the components are then cleaner. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH REFRIGERANT R134A .
When blowing, working pressure must not exceed a maximum of 217 psi (15 bar), (also use a pressure reducer for compressed air if necessary).
-- Always flush components in direction opposite of refrigerant flow direction.
Restrictor, expansion valve, compressor, receiver and reservoir cannot be flushed with compressed air and nitrogen.
-- Remove dryer cartridge on condensers with dryer.
-- First blow out dirt with compressed air, then remove moisture from components with nitrogen.
-- Connect adapter to connect the pressure hose to the refrigerant circuit. Refer to ADAPTER FOR ASSEMBLING FLUSHING CIRCUIT and [For engine(s) BGP, BPY, BGQ, CBTA, CBUA, CCTA, CBFA] Removal and Installation .
Note the following points to prevent oil and moisture from entering the refrigerant circuit from the compressed air system.
- The compressed air must be routed through a compressed air purifier for cleaning and drying. Use is therefore to be made of filter and dryer for compressed air (included in scope of delivery as tool for painting work).
- For refrigerant lines with threads or union nut at connection, make use of Adapter -V.A.G 1785/1- up to Adapter -V.A.G 1785/8- for connection of 5/8" -18 UNF charging hoses. These adapters can be found in VW/Audi passenger vehicle adapter chest -VAS 6338/1- and Commercial vehicle adapter chest -VAS 6338/50-.
- On refrigerant pipes without thread or union nut on the connection, use adapter from VW/Audi passenger vehicle set adapter chest -VAS 6338/1- as well as Commercial vehicle adapter chest -VAS 6338/50- or a standard blower pistol with rubber mouthpiece.
Compressed air/nitrogen emerging from components is to be drawn off by way of an appropriate system (for example workshop extraction system).
Certain contaminants cannot be removed or can only be removed insufficiently from the refrigerant circuit with compressed air. These contaminants can only be removed by flushing with refrigerant R134a. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH REFRIGERANT R134A .
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.