Refrigerant Circuit, Cleaning With Compressed Air And Nitrogen: Notes
This method is to be used in order to cleanly force out moisture and other contaminants as well as old refrigerant oil from the refrigerant circuit as efficiently as possible, without wasting refrigerant. In the refrigerant circuit is to be cleaned (flush with refrigerant R134a or blow through with compressed air and nitrogen)
For the most part, cleaning the refrigerant circuit with compressed air and nitrogen requires significantly more work than cleaning (flushing) with refrigerant R134a. When cleaning (flushing) with refrigerant R134a, the components are cleaned better. For this reason, always flush in case of a complaint (blowing through should only be used for certain complaints and individual components).
Under certain conditions, it may be sufficient to blow through certain components (for example, individual refrigerant lines or refrigerant hoses) with compressed air and nitrogen (for example, for purposes of forcing out old refrigerant oil from individual components that were removed).
Certain contaminants cannot be removed from the refrigerant circuit with compressed air, or can only be insufficiently removed. These contaminants can be removed, for example by cleaning (flushing) with refrigerant R134a. Refer to REFRIGERANT CIRCUIT, CLEANING (FLUSHING) WITH REFRIGERANT R134A .
When blowing through, the maximum work pressure of 15 bar (217.56 psi) must not be exceeded (corresponds to the pressure that is reached in a filled refrigerant circuit at an ambient temperature of approximately 60 °C (140 °F); if necessary, also use the pressure reducer for compressed air)
- Nitrogen can leak uncontrolled from the cylinder.
- Only use pressure reducers for nitrogen cylinders (maximum work pressure 15 bar (217.56 psi)).
- Use appropriate extraction units to draw off the gas mixture escaping from the components.
-- Always flush or blow through components in opposite refrigerant flow direction.
The compressed air and nitrogen cannot be blown through the restrictor, expansion valve, A/C compressor and receiver/dryer and reservoir.
-- For condensers, on which a dryer cartridge is installed in the integrated receiver/dryer, the dryer cartridge must be removed.
If the receiver/dryer or dryer cartridge is integrated in the condenser, they cannot be replaced separately and the condenser must be replaced after cleaning (flushing).
Depending on the version, there may be an additional filter element on receiver/dryers where the dryer cartridge can be replaced separately. This filter element must be replaced with the dryer cartridge if necessary.
-- First blow out the old refrigerant oil and dirt using compressed air and then use nitrogen to remove moisture from the components.
-- Adapter for connecting the pressure hose to the refrigerant circuit. Refer to A/C SERVICE STATION, CONNECTING .
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 cleaning device for cleaning and drying. Therefore use the filter and dryer for the compressed air (included in delivery package as a tool for paint work).
-- For refrigerant lines with thread or a union nut on the connection, use the adapter from the A/C Adapter Set:V.A.G 1785 (A/C Adapter Set - Adapter 1:V.A.G 1785/1 through A/C Adapter Set - Adapter 8:V.A.G 1785/8 ) to connect the 5/8" 18 UNF charging hoses (part of this adapter is also found in the Refrigerant Circuits Adapter Set 1:VAS 6338/1 .
-- For refrigerant lines without thread or a union nut on the connection (for connecting adapters), use the adapter from the Refrigerant Circuits Adapter Set 1:VAS 6338/1 or a commercially available air blow gun with a rubber mouthpiece.
Only use compressed air and nitrogen to clean the refrigerant circuit if it is not possible to clean (flush) the refrigerant circuit with refrigerant R134a, or the amount of work to flush individual components would be too excessive (for example, a small amount of contaminants and moisture can also be blown out of the refrigerant lines without requiring a lot of time).
Compressed air or nitrogen coming out of components is to be extracted via an appropriate system (for example, workshop extraction system).
The refrigerant circuit (or individual components) must be blown through, if there is no option for cleaning (to flush with refrigerant R134a), or cleaning (flushing with refrigerant R134a) is not practical:
-- If dirt or other contaminants are located in individual components of the circuit.
-- If the vacuum reading is not maintained when evacuating a leak-free refrigerant circuit (pressure build-up due to moisture in the refrigerant circuit).
-- The refrigerant circuit has been left open for longer than normal (for example, after a collision).
-- Pressure and temperature measurements in the circuit indicate that there is moisture in the refrigerant circuit.
-- If there is any uncertainty as to how much refrigerant oil is in the refrigerant circuit.
-- The A/C compressor had to be replaced due to internal damage (for example, noise or no output).
For vehicles with an electrically-driven A/C compressor, pay attention to the notes for replacing the Electrical A/C Compressor -V470- (the refrigerant circuit does not always have to be cleaned if there is damage to the A/C compressor electronics). Refer to A/C COMPRESSOR, REPLACING WITHOUT THE NEED FOR FLUSHING REFRIGERANT CIRCUIT .
-- If it is stipulated by the vehicle-specific repair information following the replacement of certain components.
Certain contaminants and old refrigerant oil cannot be removed from the refrigerant circuit with compressed air, or can only be insufficiently removed. These contaminants can be removed, for example by cleaning (flushing) with refrigerant R134a. Refer to REFRIGERANT CIRCUIT, CLEANING (FLUSHING) WITH REFRIGERANT R134A .