Chevrolet 1977 light duty truck, Service Manual

Page: 76 / 861

5. T E M P control set at " C O L D " and all air
c o n d itio n in g outlets open.
6. G a u g e set installed.
7. System settled out (run-in approxim ately 10
minutes).
8. A th erm o m eter placed in front o f vehicle grille
an d an o th e r in the right h a n d diffuser outlet.
N O T E : On O verh ead Systems, place a third
th e rm o m e te r in the rear unit center outlet.
9. An 18" fan placed in front o f the vehicle and
blowing into the condenser.
N O T E : H igher tem p eratu res and pressures will
occur at higher am b ie n t tem peratures. In areas o f
high humidity it is possible to have therm om eter
and gauge readings a p p ro ach but not reach the
figures listed in the pe rfo rm a n c e tables and still
have a satisfactory o p e ra tin g unit. However, it is
im p o rta n t to re m e m b e r that low pressure has a
direct relationship to nozzle outlet tem perature. If
pressure is too low, ice will gradually form on the
e v a p o ra to r fins, restricting air flow into the
passenger area and resulting in insufficient or no
cooling.
P E R F O R M A N C E D A TA
The following P erfo rm an ce D ata define norm al
o p e ra tio n o f the system u n d e r the above conditions.
Relative hum id ity does not a p p e a r in the tables because
a fte r
ru n n in g the prescribed length o f time on
recirculated air and m ax im u m cooling, the relative
h um idity o f the air passing over the evaporator core will
re m a in at approxim ately 35% to 40% regardless o f the
a m b ie n t tem p eratu re or hum idity.
C H E C K IN G OIL
In the six cylinder com pressor it is not recom ­
m ended that the oil be checked as a m atter o f course.
Four-Season A ir Conditioning (C-K Models)
(R efrig eran t Charge - 3 Lbs.
- 1 2 o z . )
T em p eratu re of
Air E ntering
C ondenser
70° 80° 90° 100° 110°
Engine rpm 2000
C om pressor Head
Pressure *
150-
205 170-
220
190-
240 220-
270 240-
290
A ccum ulator
Pressure *
20-
26 20-
28 21-
29 22-
30 23-
32
Discharge Air
Tem p, a t R ight
Hand O u tlet *
41-
47 41-
47 42-
50
43-
51 43-
51
Overhead Syste m (C -K Models)
(R e frig e ra n t C harge - 5 lb s.-4 o z .)
T e m p e ra tu re o f
A ir E n terin g
C o n d en ser 70° 80° 90° 100° 110°
E ngine rp m 20 0 0
C o m p resso r
H ead
P ressure *
135-
185
160-
210
195-
245 230-
280 270-
3 20
A c c u m u la to r
P ressu re *
22-
28 22-
30 30-
38 33-
41
37-
47
D ischarge A ir
T em p , a t R ig h t
H and O u tle t *
42-
48 42-
48 50-
58 54-
62
57-
67
R e a r C e n te r
O u tle t *
43-
49 47-
53
50-
58 55-
63
58-
68
C 6 0 System (G Models)
(R e frig e ra n t Charge — 3 l b s .)
T e m p e ra tu re o f
A ir E n terin g 70° 80° 90° 100° 110° 120°
C ondenser
E ngine rp m 2 0 0 0 RPM
C om pressor
10 20 1 4 0 - 1 6 0 - 1 9 0 - 2 1 0 -
H ead Pressure*
60
70
190
210 24 0 2 6 0
S u ctio n 3 - 3 - 3 - 4 - 7 - 1 0 -
Pressure* 9 9 9 10 14 18
D ischarge A ir
T em p , a t R ight
U pper O u tlet*
42
48 4 2 -
48
4 3 -
49
4 5 -
57
4 9 -
56
5 3 -
60
Generally, compressor oil level should be checked only
w here there is evidence o f a m ajor loss o f system oil such
as might be caused by:
• A broken re frig eran t hose
• A severe hose fitting leak
• A very badly leaking compressor seal
• Collision d a m a g e to the system com ponents
As a quick check on compressor oil charge, operate
the engine at idle on m axim um cold for approxim ately
10 minutes, turn off the engine and m om entarily crack
open the oil d ra in plug on bottom o f the compressor
letting a slight a m o u n t o f oil d ra in out. Retighten plug.
A gain slightly crack open the plug. If oil comes out, the
compressor has the required a m o u n t o f oil.