Audi Q7: Refrigerant Circuit, Flushing with Compressed Air and Nitrogen
General Information
Vehicles with a High Voltage System (Hybrid Vehicles)
Extremely Dangerous Due to High-Voltage
The high-voltage system is under high-voltage. Death or serious bodily injury by electric shock.
- Individuals with electronic/medical life- and health sustaining machines in or on their person cannot perform any work on high-voltage systems. Life- and health sustaining machines are for example pain killer pumps, implanted defibrillators, pacemakers, insulin pumps, and hearing aids.
- Have the high-voltage system de-energized by a qualified person.
There is a Risk Of Injury from the Engine Starting Unexpectedly
On electric - hybrid vehicles an active ready mode is difficult to identify. Parts of the body can be clamped or pulled.
- Turn off the ignition.
- Place the ignition key outside of the vehicle interior.
Risk of Damaging the High-Voltage Cables
Misuse can damage the insulation of high-voltage cables or high-voltage connectors.
- Never support objects on the high-voltage cables and the high-voltage connectors.
- Never support tools on the high-voltage cables and the high-voltage connectors.
- Never sharply bend or kink the high-voltage cables.
- When connecting pay attention to the coding of the high-voltage connectors.
- For all procedures on vehicles with high-voltage system pay attention to the additional warning message for these vehicles. Refer to → Chapter "Warnings when Working on Vehicles with High Voltage System".
- If procedures are necessary near components of the high-voltage system "perform a visual inspection of the damage of the high-voltage components and lines". Refer to → Chapter "Performing a Visual Inspection of Damage to High Voltage Components and Cables".
- If work on the components of the high-voltage system is necessity, de-energize the high-voltage system. Refer to → Rep. Gr.93; High-Voltage System, De-Energizing or → Electrical Equipment; Rep. Gr.93; High-Voltage System, De-Energizing.
- Charge the vehicle battery, for example, using the Battery Charger -VAS5904- in the battery support mode to minimize the number of automatic starts during the test- and measuring procedures while the ready mode is active. Refer to → Electrical Equipment General Information; Rep. Gr.27; Battery; Charging the Battery and → Electrical Equipment; Rep. Gr.93; General Notes for Working on the High Voltage System.
- Move the selector level into position "P", activate the parking brake and arrange the necessary tools for testing and measuring procedures that require the ready mode to be active or that require the ignition to be on, so that they cannot come into contact with the turning components in the engine and so that they are not in the vicinity of the turning components of a running engine.
Note
- Also move the selector lever into position "P" and activate the parking brake for testing and measuring procedures which require the ignition to be on, but do not require the ready mode to be active.
- The ready mode is displayed in the Instrument Cluster Control Module -J285- above the "powermeter". Refer to Owner's Manual.
- Activate and deactivate the ready mode. Refer to Owner's Manual (consult the display in the Instrument Cluster Control Module -J285-).
All vehicles
Compressed air and nitrogen are to be used in order to force out moisture and other contaminants as well as old refrigerant oil 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 )
Note
- For the most part, blowing through the refrigerant circuit with compressed air and nitrogen requires significantly more work than cleaning (flushing) with refrigerant R134a. As cleaning (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 conditions it may be sufficient to blow through certain components (e.g. individual refrigerant lines or refrigerant hoses) with compressed air and nitrogen (e.g. for purposes of forcing out old refrigerant oil from individual components that were removed).
- Certain contaminants cannot or can only be insufficiently removed from the refrigerant circuit with compressed air, these contaminants can be removed, for example by cleaning (flushing) with refrigerant R134a. Refer to → Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant R134a".
- When blowing through, the maximum work pressure of 15 bar (217 psi) must not be exceeded (corresponding to pressure that is reached in a filled refrigerant circuit with an ambient temperature of approximately 60 ºC (140 ºF), if necessary use pressure reducer also for compressed air)
WARNING
- Nitrogen can leak uncontrolled from the cylinder.
- Make exclusive use of pressure reducers for nitrogen cylinders (maximum work pressure 15 bar (217 psi) ).
- Use appropriate extraction units to draw off gas mixture escaping from components.
- Always flush components in direction opposite to refrigerant flow.
Note
Restrictor, expansion valve, compressor, receiver and reservoir cannot be flushed with compressed air and nitrogen.
- Remove this dryer cartridge on condensers that have one installed in the integrated receiver/dryer.
Note
- If the receiver/dryer or dryer cartridge is integrated in the condenser, then they cannot be replaced separately and the condenser must be replaced after cleaning (flushing).
- Receivers/dryers where it is possible to replace the dryer cartridge have an additional filter, which must also be replaced with the dryer cartridge.
- First flush out old refrigerant oil and dirt using compressed air and then use nitrogen to remove component moisture.
- Adapter for sealing off the pressure hose to the refrigerant circuit. Refer to → Chapter "A/C Service Station, Connecting".
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. For this reason use the filter and dryer for the compressed air (included in scope of delivery as tool for painting work).
- On refrigerant lines with thread or union nut on the connection, use the adapter from the A/C Adapter Set -VAG1785- (A/C Adapter Set - Adapter 1 -VAG1785/1- through A/C Adapter Set - Adapter 8 -VAG1785/8-) to connect charge hoses 5/8" -18 UNF (a section of this adapter is also contained in the Refrigerant Circuits Adapter Set 1 -VAS6338/1-.
- On refrigerant lines without thread or union nut on the connection (for connecting adapters), use adapter from Refrigerant Circuits Adapter Set 1 -VAS6338/1- or a standard blower pistol with rubber mouthpiece.
Note
- Only blow through refrigerant circuit with compressed air and then with nitrogen if there is no possibility of cleaning (flushing) the refrigerant circuit with refrigerant R134a or the amount of work to flush individual components becomes excessive (for example minor contaminants and moisture can also be blown out of the refrigerant lines in a short period of time).
- Compressed air/nitrogen emerging from components is to be drawn off by way of an appropriate system (for example, a workshop extraction system).
The circuit (or individual components) must be blown through (if there is no possibility for cleaning or flushing with refrigerant R134a is not recommended):
- In the event dirt or other contaminants are located in 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).
- The 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.
- 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 (for example, noise or no output).
Note
Pay attentions when replacing the Electrical A/C Compressor -V470- on vehicles with electrically driven A/C compressor (if the electronic on the A/C compressor is damaged the refrigerant circuit must not always be cleaned. Refer to → Chapter "Compressor, Replacing without the Need for Flushing Refrigerant Circuit".
- If it is stipulated by the vehicle-specific repair manual following the replacement of certain components.
Note
Certain contaminants and old refrigerant oil cannot or can only be insufficiently removed from the refrigerant circuit with compressed air, these contaminants can be removed, for example, by cleaning (flushing) with refrigerant R134a. Refer to → Chapter "Refrigerant Circuit, Cleaning (Flushing), with Refrigerant R134a".
Refrigerant Circuit, Flushing
Note
- In the case of vehicles on which the refrigerant lines have no threads for connection of Adapter Set -1785-. Use for example a flushing gun with rubber end piece or an adapter from the Refrigerant Circuits Adapter Set 1 -VAS6338/1- for blowing through the individual components. When using a flushing gun with rubber end piece, take special care 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 clean (flush or blow) components in direction opposite to refrigerant flow.
- Check expansion valve and replace if dirty or corroded.
- Locate any components on which dark, sticky deposits cannot be removed with compressed air and either clean (flush) them using refrigerant R134a or replace them.
- Thin, light grey deposits on the inside of pipes do not impair the function of the components.
- After flushing, always replace receiver/dryer or reservoir and restrictor. Replace the dryer cartridge on condensers that have one installed in the integrated receiver/dryer.
- If the receiver/dryer or dryer cartridge is integrated in the condenser, then they cannot be replaced separately and the condenser must be replaced. Refer to the Parts Catalog and → Heating, Ventilation and Air Conditioning; Rep. Gr.87; System Overview - Refrigerant Circuit (vehicle-specific repair manual).
- Receivers/dryers where it is possible to replace the dryer cartridge have an additional filter, which must also be replaced with the dryer cartridge.
After Blowing through the Refrigerant Circuit:
- Replace these components depending on equipment (restrictor and reservoir, expansion valve and receiver/dryer or dryer cartridge). Refer to → Heating, Ventilation and Air Conditioning; Rep. Gr.87; System Overview - Refrigerant Circuit (vehicle-specific repair manual) and the Parts Catalog.
- Replace the A/C compressor, depending on its condition. Refer to → Heating, Ventilation and Air Conditioning; Rep. Gr.87; A/C Compressor (vehicle-specific repair manual) and Parts Catalog or drain the rest of the refrigerant oil still inside the removed A/C compressor (replace the refrigerant circuit components) and will new refrigerant. Refer to → Chapter "Refrigerant Circuit Components, Replacing" and → Chapter "Approved Refrigerant Oils and Capacities" (Approved Refrigerant Oils and Capacities).
Note
- There is a defined and prescribed amount of refrigerant oil in the replacement compressor. If the vehicle has two evaporators, then there refrigerant circuit requires a specific quantity of refrigerant oil. Refer to → Heating, Ventilation and Air Conditioning; Rep. Gr.87; System Overview - Refrigerant Circuit (vehicle-specific repair manual) and → Chapter "Approved Refrigerant Oils and Capacities". (Approved Refrigerant Oils and Capacities).
- If the A/C compressor is not be replaced, the quantity of refrigerant oil in the A/C compressor must be topped off to the prescribed capacity (tilt the refrigerant oil out and refill the prescribed quantity into the A/C compressor or refrigerant circuit). Refer to → Chapter "Refrigerant Circuit Components, Replacing" (replacing refrigerant circuit components) and → Chapter "Approved Refrigerant Oils and Capacities". Approved Refrigerant Oils and Capacities).
- Reassemble the refrigerant circuit completely. Refer to → Heating, Ventilation and Air Conditioning; Rep. Gr.87; System Overview - Refrigerant Circuit (vehicle-specific repair manual).
- Evacuate and recharge the refrigerant circuit according to specification. Refer to → Chapter "Refrigerant Circuit, Discharging with Service Station" and → Chapter "Refrigerant Circuit, Charging with Service Station".
- Start up A/C system according to specification. Refer to → Heating, Ventilation and Air Conditioning; Rep. Gr.87; Refrigerant Circuit; A/C System, Starting Operation after Filling Refrigerant Circuit (vehicle-specific repair manual) and → Chapter "A/C System, Operating after Charging".
