GMC 4000 Series Service Manual page 87

Sec. 1
Page 80_________________
AIR CONDITIONING
Ambient A ir in Degrees F. (In A u xiliary
Fan Air Blast 2" Ahead of Condenser).
A ir Quality
Average Compressor Head
P ressu re— PSI
Average Suction Throttling Valve
Pressu re— PSI
Center Outlet Tem perature Degree F.
Shown in the above table are the average readings expected in arid or dry air, and in humid or moist air with maximum allowable tolerance
shown.
provide an internal pressure at slightly above
atm ospheric.pressure.
ASSEMBLY
1. All precautions should be taken to prevent
damage to fittings or connections. Even minute
damage to a connection could cause it to leak.
2. Any fittings getting grease or dirt on them
should be wiped clean with a cloth dampened with
alcohol. Do not use chlorinated solvents such as
trichloroethylene for a cleaning agent, as they are
contaminants. If dirt, grease or moisture gets in­
side the hoses and cannot be removed, the hose
should be replaced.
3. Sealing caps should be removed from sub-
assem blies just prior to making connections for
final assembly.
4. Use a small amount of clean refrigeration
oil (525 or 1000 viscosity) on all tube and hose
joints, and dip the O-ring gasket (when used) in
this oil before assembling the joint, as this oil will
help in making a leak-proof joint.
5. Do not connect the receiver-dehydrator as­
sembly until all other sealed sub-assem blies have
G M C S E R V I C E M A N U A L
TEST READINGS
70 80
Arid Humid Arid
125/155 150/180 160/190 180/210
20/23 21/24 20/23 22/25
41/44 48/52
44/48 53/57
Humid air is considered 20—90% R.H. Nozzle
A rid a ir is co n sid e re d 5— 20% R.H. Nozzle
Figure 9 — Operational Test Data Chart
been connected. This is necessary to insure opti­
mum dehydration and maximum moisture protec­
tion of the refrigeration system.
CAUTION - LIQUID INDICATOR (SIGHT GLASS)
drator will show clear with about 3 pounds of re­
frigerant in the system . However, the air condi­
tioner will not produce its best performance until
3 -1/4 pounds of refrigerant are in the system . Do
not overcharge with refrigerant, as this will result
in extremely high head p ressures and the com ­
pressor safety valve will "blow."
system is operating properly and efficiently, it must
be performance tested. The first step to diagnosing
a system that has been malfunctioning should be a
complete performance test (see fig. 9).
charge of refrigerant is in the system and that it
is functioning properly.
90
Humid Arid Humid
197/227 213/243 225/255
21/24 25/28 24/27
48/52 58/62 52/57 62/68
Under normal conditions, the receiver-dehy­
PERFORMANCE TESTING
In order to determine if an air conditioning
Correct pressures indicate that the required
100
Arid Humid Arid
250/280 270/300 290/320
29/32 28/31 36/39
58/65 68/75
110
Humid