Saab 900 Service Manual page 29

Heating and venti lation. system , air conditioning system 854-17
Delco compressor, 1980 models
Saab
~oo
Compressor with magnetic clutch
1 Crankcase, low-pressure side
2
Piston and valves
(4)
3
Cylinder valves
(4)
4 High-pressure side
5 Low-pressure inlet
6
High-pressure outlet
7 12 V connection
8
Field coil
9 Magnetic clutch
10 Crankshaft
7 8
S 6935
The cycling system compressor is stamped
with model no. 1131331.
Caution
Do not confuse this compressor with the
compressor for the VIR system which has
exactly the same external appearance.
The pressure-sensitive switches in these
compressors have entirely different func-
tions.
5
The compressor pressurizes the refrigerant and
forces it through the system. The pressure and
temperature increases occurring in the compres-
sor enable condensation of the refrigerant to
take place in the condenser. The compressor is a
four-cylinder unit of centrifugal design. The pis-
tons and cylinders incorporate valves that open
and close as a result of the pressure differences
caused by the reciprocating movement of the
pistons.
A pressure-sensitive switch is provided on the
high-pressure side of the compressor to protect
it from damage by overheating. In normal opera-
tion the compressor's magnetic clutch is earthed
through this switch.
If the vapour pressure drops below 40 Ib/in
2
(2.8
kgf/cm
2
),
which can occur if there is insufficient
refrigerant in the system or if the ambient temp-
erature drops below 6.5°C (44°F), the switch
breaksthe circuittothe electro-magnetic clutch.