Refrigerant Circuit, Flushing With Refrigerant R134a

Refrigerant Circuit, Flushing With Refrigerant R134a

- Flush refrigerant circuit using refrigerant R134a in order to force out moisture and other contaminants (e.g. shavings from a malfunctioning compressor) 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.

Flush the refrigerant circuit:
- In the event of dirt or other contamination in 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 following replacement of certain components.

Tools required
- A/C service station with flushing equipment VAS 6336 or A/C service station with flushing equipment VAS 6337 (these A/C service stations include the additional function for "flushing the refrigerant circuit" and the required equipment for flushing refrigerant circuits)
- Adapter case for VW/Audi passenger cars VAS 6338/1

NOTE:
- If there is neither of the mentioned A/C service stations, it is possible to flush the refrigerant circuit using flushing equipment for refrigerant circuits VAS 6336/1 or flushing equipment for refrigerant circuits VAS 6337/1 depending on the A/C service station used, flushing must then be performed manually.
- On vehicles with threaded connections to the refrigerant circuit, the adapters V.A.G 1785/7 and adapters V.A.G 1785/8 from the adapter case for VW/Audi passenger cars VAS 6338/1 can be used; on vehicles with threaded connections to compressor and to reservoir, the adapter V.A.G 1785/8 is needed twice.
- There is also a fill hose VAS 6338/31 with connections 5/8 -18 UNF and large inner diameter in short version (commercially available) included in the adapter case for VW/Audi passenger cars VAS 6338/1.

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

On a vehicle with restrictor and reservoir
- Remove restrictor (vehicle-specific) and reconnect lines.
- Remove reservoir (vehicle-specific) and reconnect the lines (use adapters and fill hose VAS 6338/31 from the adapter case for VW/Audi passenger cars VAS 6338/1 ).

NOTE: The reservoir could be flushed but because of its large internal volume it will take too much refrigerant, the reservoir would ice-up too much when extracting the refrigerant, the refrigerant would evaporate too slowly and extraction would be extended too much.

On a vehicle with expansion valve and fluid reservoir
- Remove fluid reservoir (vehicle-specific) and reconnect the lines (use adapters and fill hose VAS 6338/31 from the adapter case for VW/Audi passenger cars VAS 6338/1 ).

NOTE:
- The fluid reservoir can be flushed depending on the version (remove dryer cartridge if necessary).
- The fluid reservoir connected to the condenser (e.g. on model Audi A3 from model year 2004) remains installed during flushing (it can be flushed due to its design and is only replaced after flushing).

- Remove dryer cartridge from vehicles with dryer partridge in fluid reservoir that is connected to the condenser (vehicle-specific), and re-seal opening on fluid reservoir.
- Remove expansion valve (vehicle-specific) and install one adapter from the adapter case for VW/Audi passenger cars VAS 6338/1.

NOTE:
- If there is no appropriate expansion valve in the adapter case for VW/Audi passenger cars VAS 6338/1, the removed expansion valve may be drilled (the old expansion valve will be replaced in most cases and therefore is no longer needed).
- Remove regulating element before drilling and drill expansion valve e.g. using a suitable drill (diameter of drill e.g. 6 mm).

- Expansion valves are available in different versions and designs. For version - A -, there must be removed components - B -, - C - and - D -. Then remove component part - E - (regulating element) from component - D -. Drill expansion valve in area - F - using suitable drill.
- For version - G -, parts - H -, - I - and - K - must be removed and then drill area - L - using suitable drill.
- Clean drilled expansion valve from drilling remains (shavings)
- Install parts - B -, - C - and - D - for version - A - or - H - for version - G -

NOTE: On vehicles with two evaporators, disconnect second evaporator circuit from first evaporator circuit and flush separately.

Flushing
- Check amount of refrigerant in A/C service station, there must be at least 7 kg of refrigerant R134a

NOTE: If necessary, switch on heating installed in A/C service station for the refrigerant container before first flushing (to increase the pressure in the refrigerant container) and switch off before first extraction during flushing.

- Drain container for used oil on A/C service station
- Connect supply line (high pressure side) of A/C service station to low pressure line to compressor (line with larger diameter) using an adapter.
- Connect return line (low pressure or intake side) of the A/C service station to the flushing equipment output of refrigerant circuits
- Connect the input of the flushing equipment for refrigerant circuits to the high pressure line toward compressor (line with smaller diameter) using an adapter.

NOTE:
- Always flush components in direction opposite to refrigerant flow with A/C system operated.
- When flushing, impurities get from the refrigerant circuit to the flushing equipment and to the A/C service station, and are retained in the filter and dryer installed there. Depending on the impurities, these components must be replaced in shorter intervals corresponding to the operating instructions on the A/C service station or the flushing equipment for refrigerant circuits. (filter of flushing equipment for refrigerant circuits after approx. 5 to 10 flushing cycles, depending on impurities of flushed refrigerant circuits).
- Depending on the kind of impurity, dirt is deposited at the sight glass of the flushing device for refrigerant circuits (old refrigerant and shavings from the compressor). Clean the sight glass after flushing if necessary, and flush the refrigerant circuit again for checking (one cycle is sufficient).
- Liquid refrigerant cannot be led through the expansion valve, restrictor and dryer bag of certain fluid reservoirs at an appropriate speed, therefore these components must be removed and replaced by adapters if necessary.
- Adapters for connecting the A/C service station and for bridging certain components of the refrigerant circuit.

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

NOTE:
- Flushing procedure must be performed according to the operating instructions of the A/C service station
- Depending on the version of A/C service station, the reservoir for used oil contains only approx. 125 cu.cm refrigerant oil; in case it should be necessary to flush a system with a larger amount of refrigerant oil, it may be necessary to drain the reservoir for used oil after the first flushing procedure of a flushing cycle.
- Observe the refrigerant that flows back from the refrigerant circuit into the A/C service station; only when the refrigerant flows clear and completely colorless through the sight glass of the flushing equipment for refrigerant circuits into the A/C service station, the refrigerant circuit is cleaned.
- When flushing, the complete amount of refrigerant oil is washed out of the refrigerant circuit (except for minor remains e.g. in the evaporator which can be neglected).
- very dirty, it may be necessary to repeat the flushing procedure (i.e. two flushing cycles with three flushing procedures each).

Process of flushing (process is performed automatically according to the A/C service station program)
- After switching on, the flushing circuit (refrigerant circuit with connecting hoses and flushing equipment for refrigerant circuits) is evacuated first and the refrigerant circuit is checked for leaks during this. (Depending on the version of the A/C service station, manually advancing may be necessary).
- A specified amount (e.g. 5 kg) of refrigerant is filled into the evacuated refrigerant circuit via the high pressure side of the A/C service station (in direction opposite to the normal flow when the air conditioning is operating, and therefore on the low pressure side of the vehicles refrigerant circuit), or refrigerant is filled up until the refrigerant circuit and the sight glasses of the flushing equipment for refrigerant circuit are completely filled with liquid refrigerant (depending on the version of A/C service station it is detected whether e.g. no refrigerant was flowing for a certain time).
- After the specified amount of refrigerant has been filled in, e.g. the heating for the flushing equipment is switched on, depending on the version of the A/C service station and the flushing equipment for refrigerant circuits (only in case, the refrigerant is extracted in the gaseous state from the flushing device for refrigerant circuits).
- After the refrigerant was extracted, the heating of the flushing device for refrigerant circuits is switched off (if present), it may occur that the refrigerant circuit is shortly evacuated again, depending on its version. After evacuation, the refrigerant extracted from the refrigerant circuit is deposited by the A/C service station.
- The procedure of filling with refrigerant, extracting (and evacuating) is repeated two times (i.e. performed three times all in all).
- Depending on the A/C service station version, the flushing circuit is evacuated after extracting for the third time.

- After the flushing procedure has ended, check the one or more sight glasses of the flushing device for refrigerant circuits; if dirty, clean according to operating instructions of the flushing equipment for refrigerant circuits or the A/C service station and repeat the flushing procedure for check (one cycle is sufficient, duration approx. 30 min.)
- Check pressure in refrigerant circuit, there must be no positive pressure in the refrigerant circuit (if necessary, shortly evacuate again).
- Remove connections to A/C service station from refrigerant circuit of the vehicle (there must be no positive pressure in the refrigerant circuit)
- Replace these components depending on equipment (restrictor and reservoir, expansion valve and fluid reservoir or dryer cartridge in fluid reservoir).
- Depending on the kind of complaint, replace compressor or drain the remaining refrigerant oil from the compressor removed (replace components of refrigerant circuit) and refill the prescribed amount of fresh refrigerant oil (Approved refrigerant oils and capacities for refrigerant oil).

NOTE:
- There is a defined and prescribed amount of refrigerant oil in the replacement compressor. If necessary, a certain amount of refrigerant oil must be filled into the circuit in addition on vehicles with two evaporators.
- If the compressor is not to be replaced, the refrigerant oil in the compressor must be topped up to the specified amount (pour out refrigerant oil and fill the prescribed amount into the compressor or the refrigerant circuit).

- Reassemble refrigerant circuit completely Heating, Ventilation and Air Conditioning.
- Evacuate and recharge refrigerant circuit according to specification.
- Start up A/C system according to specification Heating, Ventilation and Air Conditioning.

Block Diagrams for Flushing Circuits

NOTE:
- The arrows in the following illustration show the refrigerant flow when flushing (when flushing, the refrigerant flows in direction opposite to the flow when the air conditioning is operating, therefore the high pressure side of the A/C service station is connected to the low pressure connection toward the compressor).
- These block diagrams indicate a refrigerant circuit with restrictor and reservoir and a refrigerant circuit with expansion valve, fluid reservoir and a second evaporator (optional equipment on certain vehicles)
- Depending on the A/C service station design, there may be check valves installed between the refrigerant circuit and the A/C service station (to ensure the correct direction of flow of the refrigerant when flushing).

Refrigerant circuit with restrictor and reservoir

NOTE: On vehicles with restrictor and reservoir, the restrictor and reservoir are removed, the lines disconnected for removing the restrictor are reconnected again. The connections to the reservoir removed are connected by means of two adapters and the fill hose VAS 6338/31 (from the adapter case for VW/Audi passenger cars VAS 6338/1 )

1 - A/C service station
- With electronics and a program for flushing, e.g. A/C service station with flushing equipment VAS 6336 or A/C service station with flushing equipment VAS 6337
- If an A/C service station with no flushing program is used, the procedure must be performed manually (evacuating, flushing 3 times with at least 4 kg refrigerant each, extracting the refrigerant, evacuating).
2 - Refrigerant hose of the A/C service station
- From the high pressure side of the A/C service station (mostly red) to the connection for the low pressure side of the compressor on the refrigerant circuit (larger diameter)
3 - Adapter for connecting low pressure side to refrigerant circuit
- Different versions depending on vehicle.
- From the adapter case for VW/Audi passenger cars VAS 6338/1
4 - Connection of low pressure side to refrigerant circuit
- Different versions depending on vehicle.
5 - Adapter for the removed expansion valve
- Different versions depending on vehicle.
- From the adapter case for VW/Audi passenger cars VAS 6338/1
6 - Evaporator
7 - Connection to fluid reservoir
- Different versions depending on vehicle.
- Neither installed on vehicles with dryer cartridge in fluid reservoir at condenser nor with fluid reservoir installed in condenser.
8 - Adapter for bridging removed fluid reservoir
- Not installed in all vehicles
- Different versions depending on vehicle.
- From the adapter case for VW/Audi passenger cars VAS 6338/1
9 - Fill hose for refrigerant.
- For example fill hose VAS 6338/31 (from the adapter case for VW/Audi passenger cars VAS 6338/1 )
10 - Condenser
- If a fluid reservoir with dryer cartridge is installed at the condenser, the dryer cartridge must be removed (reseal fluid reservoir at or in condenser).
- If the fluid reservoir is directly installed at the condenser, the fluid reservoir must be removed and replaced only after flushing
11 - Connection of high pressure side to refrigerant circuit
- Different versions depending on vehicle.
12 - Adapter for connection of high pressure side on refrigerant circuit
- Different versions depending on vehicle.
- From the adapter case for VW/Audi passenger cars VAS 6338/1
13 - Fill hose to flushing device for refrigerant circuits
- From connection to high pressure side of compressor on refrigerant circuit (smaller diameter) to input of flushing device for refrigerant circuits.
14 - Flushing equipment for refrigerant circuits
- Different versions and different designs, e.g. flushing equipment for refrigerant circuits VAS 6336/1 or flushing equipment for refrigerant circuits VAS 6337/1
- With filter, sight glass, safety valve, heating, refrigerant vessel etc. (depending on version).
- Depending on the A/C service station design and the flushing device for refrigerant circuits, there may be a check valve installed at the output of the flushing device for refrigerant circuits (to ensure the correct flow direction of the refrigerant when flushing).
15 - Refrigerant hose of the A/C service station
- From the low pressure side of the A/C service station (mostly blue) to the output of the flushing device for refrigerant circuits.
16 - Adapter to seal output to second evaporator
- Only necessary on certain vehicles with optional equipment "second evaporator"
- From the adapter case for VW/Audi passenger cars VAS 6338/1
17 - Adapter to seal output to second evaporator
- Only necessary on certain vehicles with optional equipment "second evaporator"
- From the adapter case for VW/Audi passenger cars VAS 6338/1
18 - Connection of low pressure side on refrigerant circuit to second evaporator
- Different versions depending on vehicle.
- Only present on certain vehicles with optional equipment "second evaporator"
19 - Connection of high pressure side on refrigerant circuit to second evaporator
- Different versions depending on vehicle.
- Only present on certain vehicles with optional equipment "second evaporator"
20 - Adapter for removed expansion valve at second evaporator
- Different versions depending on vehicle.
- Only present on certain vehicles with optional equipment "second evaporator"
- From the adapter case for VW/Audi passenger cars VAS 6338/1
21 - Second evaporator
- Only present on certain vehicles with optional equipment "second evaporator"

Adapter for Assembly of Flushing Circuits
- The following table lists the different adapters necessary for the connection of the A/C service station to the refrigerant circuit, flushing and bridging of the removed fluid reservoir or reservoir and the expansion valve (vehicle-specific).
- Connect the two adapters that were installed when reservoir or fluid reservoir was removed (included in adapter case for VW/Audi passenger cars VAS 6338/1 ) with a fill hose with connections 5/8 -18 UNF (short version e.g. fill hose VAS 6338/31 ).
- If a flushed refrigerant circuit is not reassembled immediately after flushing, adapters remain at connections and seal the connections at the adapters using shipping caps VAS 6338/30 (from adapter case for VW/Audi passenger cars VAS 6338/1 ).
- Depending on the version of the compressor and time period of production, different connection and sealing techniques can be found for the refrigerant circuit Heating, Ventilation and Air Conditioning.

Block or threaded connections
- Threaded connection - A -
- lock connection - B -

Block connections with various types of sealing

- Block connection with radially sealed connection - A - (with plastic or metal guide - B - )
- Block connection with axially sealed connection - C -

Audi A3, Audi TT and Audi A2

Audi 80, Audi 90, Audi Coupe, Audi Cabriolet and Audi A4

Audi 100, Audi A6, Audi Allroad and Audi V8

Audi A8

Audi Q7

NOTE: In vehicles with two evaporators, refrigerant circuit is flushed in two work steps.