Saab 900 Service Manual page 46

854-34
Heating and ventilation system, air conditioning system
Fault-tracing block diagram for Cycling Clutch
The system cools Inadequately or not at all
First:
• Check the belt tension.
• Check that the condenser Is clean.
• Start the engine. Set the air distribution control at AC max.
• Check that air is evacuated from the panel vents.
• Check that the compressor switch tums
ori
and off when the air
distributor control Is tUrned from AC max, to 0 and back. Up to and
Including 1980 models.
• Check that the compressor clutch engages and disengages
when the switch Is depressed (as from 1981 models).
I
I
Preparation:
lfthere Is no refrigerant In the system.
- Set the idling speed at
1500
r.p.m.
Ule
compreSSOf
will
not start.
- Open the right hand door(do not place the car in direct sunlight)
I
ji
Check the sight glass for visible bubbles
I
I
I Visible bubbles I
I
No visible bubbles
I
I
I
I nsufficient refrigerant.
The system is either full of refrigerant,
- Check the system for leaks.
over-full or emptY.
- Seal the leaks.
Check that the compressor pipe on the
- Discharge the system, see page 854-38 high-pressure side is warm and the low-
- Charge the system, see page 854-38
pressure pipe is cold.
- Start the unit and check that the If not, discharge the system and re-
system is sealed. charge it.
I
I
The system cools normally The system still cools insuf-
ficiently or not at aiL
Connect the high- and low-pressure gauges (idling
No
Check whether the exterior
speed 1500 r.p.m.).
of the evaporator is covered
I I
I
with ice_
Low pressure on low- Normal pressure on
High pressure on low-
Yes
I
pressure side
« 14 low-pressure side (21- pressure side (>36 psi, Check that the anti-frost thermostat
psi,
1.0
kp/cm
2 )
28
psi,
1.5-2.0
kp/cm
2
2.5
kp/cm 2 )
capillary is correctly situated in the
I I I
evaporator.
Continue at A. Check the pressure
Continue at B,
I
page 854-35 .
on the high-pressure
page 854-35 Capillary correctly positioned.
side
I
I I
Replace anti-frost thermostat.
Low pressure on the high-pressure
Normal pressure on the high-
sie
«142
psi,
10
kp/cm
2 )
pressure side
(149-220
psi,
I
10.5-15.5
kp/cm
2 )
I
Discharge the system and remove
The air-conditioning system is
the expansion valve. Check wheth-
correct. Check that the heating
er the valve filter is blocked. Clean
system water valve closes complete
and check if the valve is clear by
-Iy. If it does the system is not com
blowing through it. If not, replace
pletely full of refrigerant. Add 7
the expansion valve. If the expan-
ozs. (2 hg) R 12 or discharge the
sion valve is correct, replace the
system and completely recharge.
receiver shell.
Saab900
I