Saab 900 Service Manual page 114

854-102 Heating and ventilation system, air conditioning system
Electrical system, Clarion, 1984 models
The magnetic clutch of the compressor is
supplied from fuse 25 (30A) in the electrical dis-
tribution box. The circuit includes
• a manual switch (169) mounted in the facia
• an anti-freeze thermostat (171) mounted on
the heater box in the interior
• a pressure switch (166) mounted on the dryer
receiver
• a temperature switch (39) located in the upper
radiator hose, and on fuel injection engines
• a microswitch (167) located on the throttle
housing.
The circuit is earthed through the compressor
mounting.
When switch (169 closes, current flows to the
radiator fan relay (156) which closes, energizing
the electromagnetic clutch on the compressor,
whereupon the radiatorfan cuts in and theACfan
relay (155) is energized; the AC fan (172) now
also cuts in. The anti-frost thermostat (171)
makes and breaks the circuit to the elec-
tromagnetic clutch, according to the surface
temperature of the evaporator fins.
Pressure switch (166) breaks the circuit if the
pressure in the system falls below 2.1 kgf/cm
2
,
which will happen if there is an insufficientquan-
tity of refrigerant in the system or if the tempera-
ture of the ambient air falls below 0.5 D C (33 D F).
Ttie thermostatic switch (39) breaks the circuit if
the temperature of the coolant exceeds 115
D
C
(239 D F). This is mainly to ensure that adequate
cooling of the engine is maintained. Microswitch
(167) 'injection engines only breaks the circuit if
the throttle butterfly opens through more than
70. This, switches off the compressor to prevent
power bejng lost on acceleration.
An idling
~peed
adjustment device (142) is con-
nected in parallel with the circuit to the elec-
tromagnetic clutch injection engines only. The
device consists of a solenoid valve which boosts
the supply of,airto the inlet manifold. Air recircu-
lation is selected manually by means of a switch
(143) on the instrument panel. Current is
supplied to the switch (169). Switch (143) ener-
gizes the solenoid valve (38), which is located on
the right-hand wheel arch, and controls the recir-
culated air shutter.
Saab900