Drainage of A/C System With RHS 850
- Lock front wheels of unit when parked in position.
Before starting, check:
- oil level in drainage unit compressor (18) and in Vacuum pump (19)
- that unit contains oil by opening drain cock (15).
- Set selector switch (11) to 'PV'.
NOTE: 'PV' = Car; 'LV' = Truck
- Check that cocks 7 and 8 are closed.
- Connect unit to single-phase, 220 V, 50 Hz grounded supply.
- Connection (9) must be plugged when using the unit on a car. Brass plug is supplied.
- Set selector switch (2) to TEST.
- Close MAIN SWITCH (1). READY indicating lamp will light.
- Connect low-pressure hose (10) (blue) to A/C system service valve. Open Schraeder valve by turning cock clockwise as illustrated.
- Set selector switch (2) to RECOVERY. Open cock (7) slowly to ensure that oil does not escape from system.
System will now be drained automatically.
NOTE: High-pressure connection (9) should be used when filling the RHS 850 with R134a from an external gas bottle. This may be carried out while the A/C system in the car is being drained through the low- pressure connection. If filling the refrigerant in liquid form, the quantity should not exceed 2 kg to avoid the risk of compressor failure.
The amount of refrigerant drained may be checked in the gauge glass (13) of the glass storage cylinder. If the unit becomes full (4 kg), the red warning lamp will light and the compressor will stop.
The RECOVERY lamp (4) will light, indicating that the compressor is running, as long refrigerant remains in the system. The lamp will go out when the system is depressurized and the compressor will stop automatically. The compressor will not restart while the pressure remains low.
The A/C system is now drained. This normally takes 20-25 minutes. When the system is empty, the low-pressure gauge (14) will indicate a partial pressure i.e. a value below 0, normally -0.2 to -0.4 bar (2.9 to 5.9 psi.
NOTE: The pressure will stabilize after approx. 5 minutes and will return to 0.
NOTE: The gauge glass (13) in the glass storage cylinder does not provide an exact indication of how much refrigerant has been drained from the A/C system, since a certain quantity always collects in the drainage unit air receiver.
NOTE: that the low-pressure gauge (14) should indicate 0 bar (see illustration).
NOTE: If the gauge indicates a partial pressure, it will not be possible to drain off oil which has been extracted with the refrigerant since air will then be drawn into the system.
Open drain cock (15) to check if oil has been extracted.
Measure the quantity of oil (in the sight glass) and top up system with the same quantity of fresh oil before charging the A/C system with refrigerant.
Filling A/C system with PAG oil
It is important that the correct grade of oil is used when changing or topping up the oil in the A/C compressor. The grade of oil may differ depending on the particular compressor installed. The PAG oils for the different compressors are shown in the table below.
The different PAG oil grades may be interchanged or mixed
Model Compressor P/N of
designation PAG oil
960, 6-cyl Sanden / 1161425-2*
SD.7H15
940, 960 Turbo Seiko-Seiki / 1161426-0*
SS-121 DS5
* 40 ml (0.42 US qt) container
NOTE: The A/C system oil must be topped up before vacuum-pumping. Always use fresh oil.
Procedure for topping up PAG (PolyAlkylene Glycol) oil in car:
Remove Schraeder valve in service valve.
Remove Schraeder valve from service valve using valve tool 951 1204. Use filling syringe (without plastic hose) supplied with unit to top up oil. Ensure that syringe is clean so that different oils are not mixed, measure quantity of oil to be added and refit Schraeder valve when finished.
Illustration, filling of oil in A/C system with R134a.
Illustration, filling of oil in A/C system with R12.
Caution: Use only thumb and index finger to tighten Schraeder valve with tool 951 1204 to prevent damage to valve seal.