Saab 900 Service Manual page 112

854-100 Heating and ventilation system, air conditioning system
Cycling Clutch
1983 models
system, 1981-
The magnetic clutch of the compressor is
supplied from fuse 18 (16A in the electrical dis-
tribution box. The circuit includes
• a manual switch (150), mounted in the facia
• an anti-frosting thermostat (171) mounted on
the heater boX'JiTthe interior
• a pressure switch (169) mounted on the dryer
receiver
• a temperature switch (168) located in the
uppenadiator hose.
• on.IA cars, a microswitch (167) located on the
intake manifold throttle housing.
The" cjrcuit is earthed through the mounting of
the rn.mpressor.
When the switch (150) closes, current is fed to
both the compressor's .magnetic clutch and -the
farr. relay (155) which closes and starts the
auxinary fan (172). Once the pressure in the sys-
tem has-,reached 2131b/in 2 (15 kg/cm 2
),
the pres-
sure switch (.166) ,closes .the. circuit to the fan
relay (1:56), which starts the radiator fan (37).
The
anti~frost-.
thermostat (171) opens and
closes the.circuitto.:the magnetic clutch depend-
ing on thetempefature on the surface of the con-
denser.
The pressure switch (169) breaks the circuit if
the pressure in the system drops below 40 Ib/in
2
(2,8 kg/cm 2
),
which occurs if there is insufficient
refrigerant in the system or if the ambient temp-
erature drops below oDe (30°F).
The thermocontact (168) breaks the circuit if the
temperature of the coolant goes above 115°e
(240°F) for any reason, primarily to ensure that
the engine receives adequate cooling. The
microswitch (167) fitted in IA cars only breaks
the circuit when the throttle opening exceeds 70.
In other words, it isolates the compressor to
avoid loss of power during acceleration.
A device (142) which increases the idling speed
of the engine is connected in parallel with the
magnetic clutch circuit. This device consists of a
solenoid which boosts the supply of air to the
inlet manifold.
Wiring diagrams 1984-, see group 3:2, Electri-
cal system wiring diagrams.
Saab900