General Information

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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 when evacuating a leak-free refrigerant circuit (pressure build-up due to moisture in refrigerant circuit).
The refrigerant circuit has been left open for longer than normal (for example, after a collision).
Pressure and temperature measurements in the refrigerant circuit indicate the likelihood of moisture.
Stipulated by the vehicle-specific Service Information Heating & Air Conditioning following replacement of certain components.

NOTE:

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 cleaned better. Refer to REFRIGERANT CIRCUIT, FLUSHING WITH R134A REFRIGERANT .

When blowing, working pressure must not exceed a maximum of 15 bar (217.55 psi), (also use a pressure reducer for compressed air if necessary).

CAUTION:

- Use a pressure reducer for the nitrogen container.

-- 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.

-- For condensers, on which a dryer cartridge is installed in the integrated receiver/dryer, the dryer cartridge must be removed.

-- 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 Heating & Air Conditioning.

Note the following points to prevent the oil and moisture from the compressor unit from entering the refrigerant circuit.

The compressed air must be routed through a compressed air purifier for cleaning and drying. Therefore, the air filter and dryer is used for the compressed air (included in scope of delivery as tool for painting work). Refer to the Workshop Equipment And Special Tools Information.

For refrigerant pipes with threads or a union nut at connection, use the A/C Adapter Set - Adapter 1:VAG1785/1 through A/C Adapter Set - Adapter 8:VAG1785/8 to connection the 5/8" -18 UNF charging hoses. These adapters are located in the Refrigerant Circuits Adapter Set 1:VAS6338/1 and Refrigerant Circuits Adapter Set 2:VAS6338/50 .

For refrigerant pipes without thread or a union nut on the connection, use adapters from the Refrigerant Circuits Adapter Set 1:VAS6338/1 or Refrigerant Circuits Adapter Set 2:VAS6338/50 or a commercially available blower pistol with a rubber mouthpiece.

NOTE:

Compressed air or nitrogen coming out of components is to be extracted via an appropriate system (for example, workshop extraction system).

Certain contaminants and old refrigerant oil 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 R134A REFRIGERANT .