Saab 900 Service Manual page 66

854-54 .Heating and ventilation syste.m, air conditioning system
Checking the pressure switch operation
Cycling clutch system (Delco, Sankyo)
The pressure switch serves primarily as a control
device for the radiator fan which is vital for the
cooling of the system. When not under pressure
the switch is open and connected in parallel with
the ordinary cooling system thermocontact.
The pressure switch range is
15.7~228Ib/in2
(11-
16 kglcm?:(WheMth.e, pr.essure.lev.e.1 on the.high-
pressure·sideYalls within this range the standard
radiator fan.:cuts· in.
After the pressure has dropped byapprox. 711b/
in 2 (5 kglcm 2 ) the radiator fan will cut out, pro-
vided that the engine coolant temperature is not
so high that the fan has been energized by the
thermocontact.
The pressure switch operation can be..c.hecked by
running the engine at idling'-speed and the sys-
tem atmaximum effect which should result inthe
auxiliary fan cutting out.
To
chec~
..the..perfo.rmance of
th~
pres-
sure switch (Clarion)
A pressure-sensing sw.itch-is mounted on the
dryer receiver. The function of the switch is to
protect the compressor against overheating. The
switch is wired in series with the power supply to
the compressor clutch. If the gas pressure is
below2.1 kgf/cm 2 , which may occur if the system
contains insufficient refrigerant or ifthe ambient
temperature is below +O.5°C, the switch will
open the circuit to the magnetic clutch.
Saab 900