Refrigerant Circuit, Flushing with Compressed Air and Nitrogen: Notes
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Refrigerant circuit must be flushed with refrigerant R134a or blown through with compressed air and nitrogen in order to remove moisture and other contaminants as well as old refrigerant oil as efficiently as possible, without wasting refrigerant, without the need for extensive assembly work and without endangering the environment.
NOTE:
- Blowing through the refrigerant circuit with compressed air or nitrogen mostly requires a significantly higher amount of 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).
- Under certain circumstances, it may be sufficient to blow through certain components (e.g. individual refrigerant lines or hoses) with compressed air or nitrogen (e.g. for pressing out old refrigerant oil of individual removed components).
- Certain impurities cannot or can only insufficiently be removed from the refrigerant circuit using compressed air, these impurities can be removed by e.g. flushing with refrigerant R134a → Refrigerant Circuit, Flushing with Refrigerant R134a
- When blowing through, the maximum work pressure of 15 bar must not be exceeded (corresponding to pressure that is reached in a filled refrigerant circuit with an ambient temperature of approx. 60 C, if necessary use pressure reducer also for compressed air)
CAUTION:
- 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 or blow through components in direction opposite to refrigerant flow.
NOTE:
- Restrictor, expansion valve, compressor, receiver and reservoir cannot be flushed with compressed air and nitrogen.
- Remove dryer cartridge on condensers on which the dryer cartridge is installed in the integrated receiver.
- First flush out old refrigerant oil and dirt using compressed air and then use nitrogen to remove component moisture.
- Adapters for connecting pressure hose to refrigerant circuit → A/C Service Station, Connecting and → 87 - Air conditioning
Pay attention to the following items to prevent oil and moisture from the compressed-air system penetrating into the refrigerant circuit.
- 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 pipes with thread or union nut at connection, make use of adapters from Adapter set refrig cir R 134a V.A.G 1785 ( adapter V.A.G 1785/1 to adapter V.A.G 1785/8 ) for connection of 5/8" -18 UNF charging hoses (part of these adapters is also included in Adapter case for VW/Audi passenger cars VAS 6338/1 ).
- For refrigerant pipes with no thread or union nut at connection (for installing adapters), make use of adapter from Adapter case for VW/Audi passenger cars VAS 6338/1 or commercially available flushing gun with rubber end piece.
NOTE:
- The refrigerant circuit is only to be blown through with compressed air and nitrogen afterwards if there is no possibility to flush the refrigerant circuit or flushing of individual components would require too much effort (it is possible to blow out minor impurities and moisture from the refrigerant pipes without much time needed).
- Compressed air/nitrogen emerging from components is to be drawn off by way of an appropriate system (workshop extraction system).
The circuit (or individual components) must be blown through (if there is no possibility for flushing or flushing is not recommended):
- In the event of dirt or other contamination in the individual components of the circuit.
- If vacuum reading is not maintained on evacuating a leak-free refrigerant circuit (pressure build-up due to moisture in refrigerant circuit).
- If refrigerant circuit has been left open for longer than normal (e.g. following an accident).
- If pressure and temperature measurements in the refrigerant circuit indicate the likelihood of moisture.
- In the event of doubt about the amount of refrigerant oil in the circuit.
- The A/C compressor had to be replaced on account of internal damage (e.g. noise or no output).
- If stipulated by the vehicle-specific repair manual following replacement of certain components.
NOTE:
- Certain impurities and old refrigerant oil cannot or can only insufficiently be removed from the refrigerant circuit using compressed air, these impurities can be removed by e.g. flushing with refrigerant R134a → Refrigerant Circuit, Flushing with Refrigerant R134a