Part 1

Refrigerant Circuit, Flushing (Cleaning) With Refrigerant R134a

- Refrigerant circuit must be flushed with refrigerant R134a in order to force out contaminants (e.g. abraded material from a malfunctioning A/C compressor) as well as old refrigerant oil as efficiently and as cleanly as possible and without the need for extensive work.

NOTE: Flushing a refrigerant circuit is shown in Volkswagen ServiceNet; API/PKW or Volkswagen TV API Online; then General Information and 08.06.05 Refrigerant circuit, flushing on Golf Plus.

The refrigerant circuit should be flushed with refrigerant R134a if:
- dirt or other contamination is in the refrigerant 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).
- If pressure and temperature measurements in the refrigerant circuit indicate the likelihood of moisture in the circuit.
- In the event of doubt about the amount of refrigerant oil in the circuit. If the A/C compressor should be reinstalled, the refrigerant should be drained from the compressor via the drain plug (replace O-ring). To facilitate this, the ribbed belt pulley or magnetic clutch plate on the A/C compressor should be rotated by hand. After flushing, the entire quantity of refrigerant oil should be added to the refrigerant circuit (50 grams directly in the A/C compressor). Note additional oil quantity for systems with a 2nd evaporator.
- A/C compressor had to be replaced on account of internal damage (e.g. noise or no output).
- stipulated by the vehicle-specific repair information, following replacement of certain components.

Tools required
- A/C service station with flushing device VAS 6380 or A/C service station with flushing device VAS 6337. The auxiliary function "Flush refrigerant circuit" and the refrigerant circuit flushing device required for it are present on these A/C service stations.
- VW/Audi passenger vehicle set adapter chest VAS 6338/1 and Workshop equipment and special tools catalog.
- Commercial vehicle set adapter chest VAS 6338/50 and Workshop equipment and special tools catalog.

NOTE:
- If neither of the two A/C service stations listed above are available for use in the workshop, Refrigerant Circuit Flushing Device VAS 6336/1 or Refrigerant Circuit Flushing Device VAS 6337/1 (depending on the workshop A/C service station version) (min. 7 kg refrigerant R134a in refrigerant bottle) can also be used to flush the refrigerant circuit. However, the flushing procedure must then be performed manually.
- In vehicles with screw-connections on refrigerant circuit, adapter V.A.G 1785/1 up to adapter V.A.G 1785/8 from VW/Audi passenger vehicle set adapter chest VAS 6338/1 or commercial vehicle set adapter chest VAS 6338/50 may be used. In vehicles with screw-connections on A/C compressor and on accumulator, two of the adapters V.A. G 1785/8 are required.
- A charging hose VAS 6338/31 with 5/8 inches - 18 UNF connections and large internal diameter can be found in the adapter chests in order to be able to bridge components (it is commercially available).

Preparation
- Discharge refrigerant circuit.
- Remove A/C compressor.

On a vehicle with restrictor and reservoir.
- Remove restrictor (specific to vehicle) and reconnect refrigerant pipes to each other.
- Remove reservoir (specific to vehicle) and connect refrigerant pipes to each other (to do this, use adapter and charge hose VAS 6338/31) from VW/Audi passenger vehicle set adapter chest VAS 6338/1.

NOTE: The reservoir could be flushed, however it requires too much fluid refrigerant due to its large internal volume. When this refrigerant is extracted, the reservoir ices up severely and this prolongs the extraction process significantly.

On a vehicle with expansion valve and fluid reservoir.
- Remove fluid reservoir (specific to vehicle, not required for all vehicles) and connect refrigerant pipes to each other (for this, use adapters and charging hose VAS 6338/31).
- Remove expansion valve (specific to vehicle) and install the adapter for it.

NOTE: If no suitable adapter for the expansion valve is available in Adapter Set for Refrigerant Circuits VAS 6338/1 or Commercial Vehicle Adapter Set Chest VAS 6338/50, the remove expansion valve can also be drilled open (the expansion valve must be replaced with a new one).

CAUTION:
- Make sure that sealing surfaces on expansion valve are not damaged when drilling open.
- Otherwise refrigerant leaks out.







NOTE:
- Several components are to be removed from expansion valve before drilling open.
- Expansion valves are available in different versions. For version -A-, components -B -, -C- and -D- must be removed. Then separate regulating element -E- from component -D-. Then drill open expansion valve in area -F- using a suitable drill (6 mm diameter).
- For version -G-, parts -H-, -I- and -K- must be removed and then drill open area -L- using suitable drill (6 mm diameter).
- Clean the drilled open expansion valve of residue from the work (shavings).
- Install parts -B-, -C- and -D- for version -A- or -H- for version -G-.
- In vehicles with two evaporators, the circuit to the second evaporator must be disconnected from circuit of the first evaporator and must be flushed via a separate work procedure.

Flushing
- Check refrigerant quantity in the refrigerant cylinder, there must be at least 7 kg of refrigerant R134a.

NOTE: If necessary, switch on the heater installed on the refrigerant cylinder for 30 minutes before the first flushing procedure. This increases pressure in the refrigerant cylinder and accelerates charging of the flushing circuit.

- Drain the old oil container of the A/C service station.
- Connect supply hose (high pressure side) of A/C service station via an adapter to the low pressure line to the A/C compressor (line with larger diameter).
- Connect return hose (low pressure- or intake side) of A/C service station to output of refrigerant circuit flushing device.
- Connect input of refrigerant circuit flushing device via an adapter to the high pressure line to the A/C compressor (line with smaller diameter).

NOTE:
- Components are always flushed in the opposite direction of refrigerant flow when A/C system is in operation.
- While flushing, contaminants from the refrigerant circuit enter the refrigerant circuit flushing device and the A/C service station and are absorbed by the filters and dryers installed there. Depending on the contaminant, these components are to be replaced in shorter intervals in line with operating instructions for A/C service station or refrigerant circuit flushing device.
- The filter in the refrigerant circuit flushing device depends on the type and degree of contamination in the flushed refrigerant circuit, it should be changed after 5 to 10 flushing cycles at the latest. If a heavily contaminated refrigerant circuit is flushed (the refrigerant oil from the circuit is black and viscous or there are many shavings in the refrigerant circuit), the filter should be replaced after flushing. With a refrigerant circuit heavily contaminated in this way, it is wise to flush the circuit again after changing the filter.
- Depending on the type of contamination, dirt (old refrigerant oil and abraded material from A/C compressor) is deposited on the viewing glass(es). Clean viewing glass(es) after flushing and flush the refrigerant circuit once more with one flushing procedure as a check.
- Fluid refrigerant cannot be conducted with the necessary speed through the expansion valve, restrictor and desiccant bag of certain fluid reservoirs, therefore these components must be removed and replaced by an adapter.
- Adapters for connecting A/C service station and for bridging certain components of refrigerant circuit.

- Switch on A/C service station and flush refrigerant circuit (duration approx. 1 to 1.5 hours for one flushing cycle with three flushing operations).

NOTE:
- Perform flushing of refrigerant circuit according to operating instructions of the A/C service station.
- Depending on A/C service station version, the old oil container holds only approx. 125 cu.cm of refrigerant oil. In the event a system with a larger volume of refrigerant oil must be flushed, it may be necessary to empty the old oil container after the first flushing procedure of a flushing cycle.
- Observe the refrigerant which flows back from the refrigerant circuit. Only when the refrigerant streams clear and completely colorless through the viewing glass(es) of refrigerant circuit flushing device in the A/C service station has the refrigerant circuit been cleaned.
- When flushing, the complete amount of refrigerant oil is washed out of the refrigerant circuit (except for minor remains which can be disregarded).
- If contamination is especially severe, it may be necessary to perform the flushing cycle twice (two flushing cycles with three flushing operations each). Before the second flushing cycle, the filter on the flushing device must be replaced.

Sequence of flushing procedure (sequence occurs automatically according to the A/C service station program)
- After switching on, the flushing circuit (refrigerant circuit with connecting hoses and refrigerant circuit flushing device) is first evacuated and the refrigerant circuit is simultaneously checked for leaks. Depending on A/C service station version, it is possible that manually switching to advance the program is required.
- A prescribed amount of refrigerant (e.g. 4 kg) is filled into the evacuated flushing circuit via the high pressure side of the A/C service station (opposite the normal direction of flow during normal A/C system operation and thus on the low pressure side of vehicle refrigerant circuit). Depending on A/C service station version, refrigerant is filled in until the flushing circuit has been completely filled with refrigerant. This can be detected by e.g. refrigerant no longer flowing in after a certain period of time.
- After the prescribed quantity of refrigerant has been filled, e.g. the heater for the refrigerant circuit flushing device is switched on (only in the event the refrigerant is extracted in gaseous form from the refrigerant circuit flushing device), depending on version of A/C service station and refrigerant circuit flushing device.
- After the refrigerant has been extracted, heater of refrigerant circuit flushing device (if present) is switched off, refrigerant circuit is possibly evacuated briefly anew depending on the version, and the refrigerant oil extracted from the refrigerant circuit is separated by the A/C service station after evacuating.
- The sequence of filling refrigerant, extracting (and evacuating) is repeated twice (performed a total of three times).
- After the third extraction, the flushing circuit is evacuated depending on the version of the A/C service station.

- After flushing cycle has ended, check viewing glass(es) of refrigerant circuit flushing device, if they are dirty, clean them in line with the operating instructions of refrigerant circuit flushing device or A/C service station. Perform one addition flushing cycle as a check. One flushing procedure is sufficient (approx. 30 min.)
- Check pressure in refrigerant circuit, there must be no positive pressure in the refrigerant circuit (evacuate refrigerant circuit briefly once more if necessary).
- Disconnect A/C service station connections from vehicle refrigerant circuit. There must be no positive pressure in the refrigerant circuit.
- Replace these vehicle-specific components.

- Restrictor and reservoir
- Expansion valve and fluid reservoir or dryer cartridge in fluid reservoir

- Depending on the complaint, replace A/C compressor or drain the remaining refrigerant oil from the removed A/C compressor (replace refrigerant circuit components) and re-fill the prescribed quantity of fresh refrigerant oil vehicle-specific.

NOTE:
- A certain prescribed quantity of refrigerant oil is in the A/C compressor original part. On vehicles with two evaporators, a certain quantity of refrigerant oil must also be added to the circuit if necessary.
- 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) (replacing refrigerant circuit components).

- Completely reassemble the refrigerant circuit.
- Evacuate and recharge refrigerant circuit according to specification.
- Start up A/C system according to specification.