Refrigerant Circuit, Flushing With Compressed Air and Nitrogen

Refrigerant Circuit, Flushing With Compressed Air And Nitrogen

- 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.

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 (e.g. following an accident).
- pressure and temperature measurements in the refrigerant circuit indicate the likelihood of moisture.
- stipulated by the vehicle-specific repair information, 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 cleaner.
- When blowing, working pressure must not exceed a maximum of 15 bar, (also use a pressure reducer for compressed air if necessary).

CAUTION:
- Nitrogen can leak uncontrolled from the cylinder.
- Make exclusive use of pressure reducers for nitrogen cylinders (maximum work pressure 15 bar).
- Use appropriate extraction units to draw off gas mixture escaping from components.

- 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 fluid reservoir, 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 and.

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) Workshop equipment and special tools catalog.
- 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 inches - 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 threads 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.

NOTE:
- Compressed air/nitrogen emerging from components is to be drawn off by way of an appropriate system (e.g. 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.

Blowing through refrigerant circuit

NOTE:
- For vehicles in which no adapters fit on to the refrigerant pipes, e.g. a blower pistol with rubber mouthpiece is to be used to blow through individual components. Special care must be taken not to damage the connections (crushing or scratching).
- Evaporator is to be flushed via the connection for low-pressure pipe (large diameter) after removing expansion valve or removing restrictor.
- Always flush components in direction opposite of refrigerant flow direction.
- Check expansion valve and replace if dirty or corroded.
- If there are dark, sticky deposits in the components that cannot be removed with compressed air, replace these components.
- Thin, light grey deposits on the insides of refrigerant pipes do not impair the function of the components.
- After flushing, always replace receiver or reservoir and restrictor. Replace dryer cartridge or dryer on condensers with attached dryer.