Chevrolet 1977 light duty truck, Service Manual

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Overhead System (G Models)
(R efrig eran t Charge — 5 lb s.-4 o z.)
T e m p e ra tu re o f
Air E n terin g
C ondenser
70° 8 0° 9 0° 100° 110° 120°
E ngine rp m 2000
C om pressor
Head Pressure*
5 0 - 1 6 0 - 2 0 0 - 2 2 5 - 2 5 0 - 2 8 0 -
2 00 2 10 2 50 275 3 00 320
S u ctio n
P ressure*
13 1 3 - 1 6 - 1 9 - 23 2 6 -
19 21 24 27 31 34
D ischarge A ir
T em p , a t R ig h t
F ro n t U pper
O u tlet*
3 8 3 8 - 3 9 - 4 5 - 5 0 - 5 4 -
44 44 47 53 58 62
R e a r sy stejn te m p e ra tu re s a t c e n te r o u tle t
ru n 5 - 1 0 higher th a n f r o n t system .
N O T E : The oil m ay a p p e a r foamy. This is
considered normal.
To fu rth er check the compressor oil charge, should
the above test show insufficient oil, it is necessary to
rem ove the compressor from the vehicle, drain and
m easure the oil as outlined u n d e r "C hecking Com pressor
Oil C h a rg e ."
C hecking Com pressor Oil Charge
1. Run the system for 10 minutes at 500-600
engine rpm with controls set for m axim um cooling and
high blower speed.
2. T u rn off engine, discharge the system, remove
com pressor from vehicle, place it in a horizontal position
with the drain plug downward. Remove the drain plug
and, tipping the compressor back and forth and rotating
the com pressor shaft, d ra in the oil into a clean container,
m easure and discard the oil.
3. A dd new refrigeration oil to the compressor as
follows.
a. If the qu an tity d ra in e d was 4 fluid oz. or
more, add the same a m o u n t o f new re frigeration oil to
the rep lacem en t compressor.
b. If the quantity d ra in e d was less than 4 fluid
oz., add 6 fluid oz. o f new refrig eratio n oil to the
replacem ent compressor.
c. If a new service compressor is being installed,
d ra in all oil from it an d replace only the am ount
specified in Steps 3a and 3b above.
d. If a field rep aired compressor is being
installed, add one additional fluid oz. to the compressor.
Dash M ounted U n it (M o to r H om e Chassis)
(R efrig eran t Charge — 3 lb s.-4 oz.)
T e m p e ra tu re o f
Air E n terin g
C ondenser
70° 80° 90° 100° 110° 120°
E ngine rpm
2000
C om pressor
Head Pressure*
1 1 0 -
120 1 3 5 -
145 1 60-
170 1 9 0 -
200
2 20-
230 2 60-
270
S u ctio n
Pressure psi*
6 7 9 10
10 13
D ischarge A ir
T e m p eratu re*
4 0 -
45 4 1 -
46 4 1 -
46 4 2 -
47 4 4 -
49
4 4 -
49
* Ju st p rio r to co m p resso r c lu tch disengagem ent.
4. In the event that it is not possible to idle the
compressor as outlined in Step 1 to effect oil return to it,
proceed as follows:
a. Remove the compressor, drain, m easure and
discard the oil.
b. If the a m o u n t drained is more than 1-1/2
fluid oz. and the system shows no signs o f a m ajor leak,
add the same a m o u n t to the replacem ent compressor.
c. If the a m o u n t drained is less than 1-1/2 fluid
oz. and the system appears to have lost an excessive
a m ount o f oil, add 6 fluid oz. o f clean refrigeration oil to
replacem ent compressor, 7 fluid oz. to a repaired
compressor.
If the oil contains chips or other foreign
m aterial, replace the receiver-dehydrator (expan­
sion tube on C-K models) and flush or replace all
com ponent parts as necessary. A dd the full
specified volume o f new refrig erato n oil to the
replacem ent compressor.
5. Add additional oil in the following am ounts for
any system com ponents being replaced.
E vap o rato r C o r e ................................... 3 fluid oz.
C o n d e n s e r .... :......................................... 1 fluid oz.
R e c e iv e r-D e h y d ra to r........................... 1 fluid oz.
A c c u m u la to r ........................................... 1 fluid oz.
C A U TIO N :
When adding oil to the compressor,
it will be necessary to tilt the rear end o f the
compressor up so that the oil will not run out o f
the suction and discharge prots. Do not set the
compressor on the shaft end.