Saab 900 Service Manual page 44

854-32 Heating'and ventilation system, air conditioning system
Fault tracing and fault-tracing
list for the Cycling Clutch
Check the following before following the fault-
diagnosis table:
• That the drive belt for the compressor is in
good condition and correctly tensioned.
• That air is entering the inside of the car
through the vents.
• That the flow of air through the condenser is
not obstructed.
• That the electromagnetic clutch for the com-
pressor cuts in and out when the AC system is
switched on - the ambient temperature must
be at least +8 or goe (46-48°F). If the com-
pressor fails to cut in, the system may be
starved of refrigerant (cut-in prevented by the
pressure switch on the receiver).
• That the AC fan cuts in when the system is
switch on.
How to use the fault diagnosis table
Ider.ltify the possible cause of the relevant
symptom (marked with 'X' in the table) .and.read
along the line. Identify all possible causes and
then decide which is the most likely. Perform all
the simple checks first. Note that the possible
causes:.aT.e,not.liste·d in any order of probability.
Symptom
.
;
'OJ)
E
'OJ)
c Cl)
.....
c
(J)
'aD 0
>.
c
(5
0 (J)
(5
0
u
c
u
u
0
Cl)
''::;
Cl)
u
:OJ
ro
(J)
0
....
.....
Ui
0
Z ::i
Z
x
x
x
x
Possible cause
Electrical faults:
Blow fuse
Poor connection or earthing
(Compressor not running)
Compressor clutch bumt out
Fan motor not running
Check/remedy
Check the fuses (if necessary, referto wiring diagram)
Check all leads
Change the clutch
Check electrical connections and fan motor
x
x
x
x
x
x
x x
x
x
x
x
Fan motor running erratically
(Play or fractured component in motor)
Break or poor contact in the compressor
clutch winding (clutch slips in and out)
Fan motorwhining ortouching
casing
Mechanical faults
Slack drive belt
Blockage in air duct
Clutch bearing worn or out of true
Compressor worn or insecurelyfitted
Saab900
Check and change if necessary
Change the clutch
Check
Adjust or change the belt
Check and clean
Change the bearing
Overhaul the compressor and tighten fixings