Chevrolet 70 Series 1970, Service Manual

Page: 151 / 841

CAB AND BODY MOUNTINGS 1-120
T E S T REA D IN G S
A m b ie n t A ir in Degrees F . (In A u x ilia ry
Fa n A i r B last 2" A h e ad o f C o n d e n s e r).
70 80 90 100
1 10
A i r Q u a lity A r id H u m id A r id H u m id
A r id H u m id A rid H u m id A r id H u m id
A v e ra g e Com pressor Head
P r e s s u r e - P S I
12 5 /15 5 15 0 /18 0 16 0 /19 0 18 0 /2 10 1 9 7 / 2 2 7 213 /2 4 3 225/255 250/280 2 70 /3 0 0 290/320
A v e ra g e Suction T h ro ttlin g V a lve
P r e s s u r e - P S I 20 /2 3 2 1 / 2 4
20 /23 22/25 2 1 / 2 4 2 5 /2 8 2 4 / 2 7 29 /3 2
2 8 /3 1 36/39
C en te r O u tle t Te m p e ra tu re Degree F . 4 1 / 4 4 48/5 2 4 4 /4 8 5 3 /5 7 4 8/5 2 58/62
5 2 /5 7 62/68 58/65 6 8 /75
S h o w n in the above tab le are the average readings expected in arid or d ry a ir, and in hu m id or m o ist air w ith m a xim u m a llow able tolerance
s how n.
H u m id air is considered 20 — 9 0 % R .H . N o zz le
A r id a ir is c o n s id e re d 5 - 2 0 % R .H . N o zz le
T-3311
Figure 19—Operational Test Data Chart
P .O .A . VALVE (ALUMINUM TILT CAB)
(R efer to F ig. 15)
The only check fo r proper P .O .A . valve oper­
ation i s to check the su ction p r e ssu r e at the valve
a s during a perform ance te s t . The P .O .A . valve is
an absolute valve and w ill provide different gauge
readings b ased on the altitude w here the readings
a r e being taken. C orrect gauge reading at s e a lev el
is 29.5 p sig . Gauge readings w ill be o n e-h alf p s i
higher for each additional
1 , 0 0 0
fe et of elevation .
The follow ing table l i s t s gauge readings at
d ifferen t a ltitu d es. If a valve g iv es im proper gauge
read in gs, it m ust be rep laced sin c e it is neither
rep airab le nor adjustable:
29.5 p sig .
30.0 p sig .
30.5 p sig .
31.0 p sig .
31.5 p sig .
32.0 p sig . — S e a le v e l
-
1 , 0 0 0
ft.
-
2 ,0 0 0
ft.
- 3,000 ft.
- 4,000 ft.
- 5,000 ft.
32.5 p s i g . — 6,000 ft.
33.0 p s i g . — 7,000 ft.
33.5 p s i g . — 8,000 ft.
34.0 p s i g . — 9,000 ft.
34.5 p sig . — 10,000 ft.
NOTE: R efer to "Insufficient Cooling D iagn osis
Chart" and "Specifications" at end of th is sectio n
fo r other pertinent air conditioning inform ation
rela ted to p erform an ce testin g .
PRELIMINARY CHECKS
1. Inspect c o m p resso r d rive b elt. Check and
adjust USED V -b e lt ten sion 80 to 90 pounds on b elt
ten sion gauge (J-23573) and 120 to 130 on NEW
b e lts . Check and adjust USED P o ly -V b elt ten sion
64 to 74 pounds on b elt ten sion gauge (J-23586) and
84 to 94 pounds on NEW belt.
2. Check a ll refrig era tio n lin e s for lea k s,
kinks, o r other r e str ic tio n s.
3. Check outer su r fa c e s of radiator and con­
d en ser c o r e s to be su re they a r e not plugged with
dirt, le a v e s o r other foreign m a teria l. B e su r e to
check betw een the condenser and radiator a s w ell
a s the outer su r fa c e s.
4. Connect engine tach om eter.
5. Start engine and op erate at 2000 rpm with
"AIR" le v e r on "OUTSIDE" and "TEMP" le v e r s e t
fo r m axim um cooling, and blow er on "HIGH." A fter
at le a s t fiv e m inutes of engine operation, o b serv e
fo r bubbling at the sigh t g la s s (above 7 0 °F . am ­
bient). If the s y s te m is low on refrig era n t, add
refrig era n t until liquid indicator just show s clea r
and add an additional K-lb. of refrig e ra n t.
6
. Under the sam e conditions a s in Step 5
p r e v io u sly , m ove "AIR COND" le v e r to "OFF."
T h is should disengage the c o m p r e sso r clutch. If
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL