Draining Air Conditioning (A/C) System

For fast draining, the A/C system (i.e. the car) should be at least at room temperature (around 20°C). In winter, the car should always be taken inside the workshop the evening before starting work. The refrigerant draining time will be less if the A/C system has recently been on and the engine is warm (radiant heat). Run the car's A/C system for five minutes before draining if possible: this will cut draining time.

Preparations before draining:








Checks:
- Chock the front wheels on the unit where they are parked. (Set handbrake)
- Check oil level in drainage unit compressor and evacuate before starting.
- Check there is no oil in the unit by opening the bleed valve (15).
- Check all valves are shut.
Settings:
- Set switch (11) to position PV.
- Connect unit to 220 V 50 Hz single-phase grounded supply.
- Connection (9) should be plugged for PV use. A brass plug is included in the kit.
No plug is needed for LV use, as both high and low pressure are connected.
- Switch unit on (1): white indicator light will come on.
- Connect low-pressure hose (10 blue) to
air-conditioning (A/C) system service valve.
- Open valve (7) slowly.
- Valve (8) should be shut while draining.

Draining:





- Turn switch (2) to "recovery" position. The unit will then drain the system automatically and is then ready for use.

NOTE: If the RHS 850 unit needs tilling with R 134a from an external gas cylinder, this should be done via the upper high-pressure connection (9). This can be done at the same time as draining the A/C system via the low-pressure connection.

- Refrigerant can be read off via the glass cylinder gauge (13). Once the unit is full, (4 kg), the red light comes on to show this and the compressor stops.
- The recovery light (4) will stay on as long as there is refrigerant in the system, to show that the compressor is working.
- Once the pressure in the system stops, the light will go out and the compressor will stop automatically. If the pressure stays low, the compressor will cut in again.
- The A/C system is now empty. This normally takes 20 - 25 min.

Once the system is empty:
Once the system is empty, the low-pressure meter (14) should show a vacuum: in other words, a figure less than 0, normally -0.2 to -0.4 bar, assuming the car has been indoors at room temperature (20 - 25 °C = 68 - 77 °F) for a few hours or the engine is warm.

NOTE: Pressure stabilizes after about 5 min and returns to "0". If the meter shows a vacuum, it will be impossible to drain off the oil which comes out when the A/C system is drained.

Topping up oil in A/C system:

Fig. 5 A/C System Fluid Level Inspection:

After about five minutes, the pressure in the unit equalizes: you can now drain any oil which has come out from the car's A/C system.
- Check the unit's drain valve (15) to see if any oil has come out of the A/C system.
- Measure the amount of oil (in the sight gauge) and top up with an equivalent amount of fresh oil. Do this before refilling car A/C system with refrigerant.

NOTE: Top up oil before pumping out.

Topping up PAG oil
To top up car with PAG oil (P/N 8708581-7):
- Undo unit top-up valve.
- Remove Schrader valve. (Use valve extractor 9811 994-4.)

Now use topping-up syringe (without plastic hose) supplied with the unit. Clean syringe out beforehand if necessary to avoid mixing different oils. Now measure how much oil needs to be topped up. After topping up oil, refit Schrader valve.

NOTE: When tightening up Schrader valve with tool 981 1994-4, use thumb and first finger only to avoid damaging Schrader valve seal.

Fault-tracing:





NOTE Cars have no high/low-pressure connections on compressor. This means only the low-pressure Pressostat can be checked to see if it is working. Connect as usual via drain/fill valve.

- Set switch (11) to position PV.
- Set switch (2) to TEST.
- Start engine and switch A/C system to on.
- The low-pressure Pressostat will now work as low-pressure meter (14).