Pontiac FIREBIRD 1972 Service Manual page 88

CUSTOM AIR CONDITIONING 1A-29
4 TH STAGE EXISTING CONDITIONS
-
PISTON CLOSES
-
h e pressure surrounding bellows and on top of piston has now increased sufficiently
over 28.5 psi to become nearly equal (within 1.3 psi) of Inlet pressure. Since
-
b
A
6)
Pressures on both sides of piston nearly
equal
-
sprlng takes over and pushes
plston closed.
5TH STAGE EXISTING CONDITIONS
-
BELLOWS OPENS
-
&
The pressure surroundina bellows and on
to^
i f Diston i s now sufficientlv over 28. 5
/
\
a ~ a c u u m Bellows
-
has contracted due to
I
@Needle Valve
-
opens again allowing com-
Increase in pressure pressor to pull pressure down in area
surrounding bellows
6 TH STAGE EXISTING CONDITIONS
-
PISTON OPENS
-
a
&
An uneaual vressure occurs because
I I
.
-
compressor i s
in
the process of pulling
outlet Dressure down
1
Piston
-
opens because pressure on
Ummm
( w e t
m)
is p e W r
m u
pre-
ssure on top of piston
I
Fig. 1A-23 P.O.A. Valve
-
Basic Operation