Saab 900 Service Manual page 54

854-42 Heating and ventilation system, air conditioning system
Disconnect the yellow hose from the vacuum
pump and insert it in the end of an exhaust ex-
traction hose. Open the valves on the compres-
sor.
Open valves C and D.
Slowly open Valve A and carefully release the
gas. Check that no liquid is visible in the sight
glass on the gauge set.
Note
If the refrigerant is allowed to discharge too
quickly, refrigerant oil may be lost.
When the reading on the gauges shows '0' bar
and the system is empty: close all valves. Recon-
nect the hose to the vacuum pump.
Charging the refrigerant
Before starting work, read through the safety
precautions carefully. Check that a sufficient
quantity of refrigerant is in the measuring cylin-
der (at least 1350 -1400 g). The scale can be ro-
tated, use the one marked R12.
The pressure in the measuring cylinder is read
from the gauge on top of the measuring cylinder.
(The pressure in the measuring cylinder will vary
with the temperature of the refrigerant.) Rotate
the R12 scale on the measuring glass to the
same value indicated on the gauge.
Example: The reading on the gauge is 4.9. Ro-
tate the measuring glass so that the 4.9 mark
comes immediately above the column of refri-
gerant.
Saab 900