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16-20
GROUP 16- VENTILATING AND HEATING
system and
damage the compressor.
In surrounding air temperatures above
90 degrees F
.,
prolonged engine idle
will result in excessively high com-
pressor pressures.
El
ADJUSTMENTS
DISCHARGING THE SYSTEM
When replacing any component
in
the air
conditioning
system, the
system must be discharged. To dis-
charge the system proceed as follows:
1. Remove the caps from the high
and low pressure service (Schrader)
valves in the high and low pressure
lines at the compressor (Fig.
18).
2. Turn
both
manifold gauge
valves
fully
clockwise to close the
gauge set to the center outlet hoses
(Fig.
19).
3.
Connect
the high and low
pressure gauge hoses with adapters,
to the respective high and low
pressure service valves at the com-
pressor
(Fig.
20).
4. Place the open end of the center
hose
in
a garage exhaust outlet.
5. Slowly depressurize the refrig-
eration system by opening the low
pressure gauge valve a slight amount
and allowing the refrigerant to dis-
charge
slowly from the system.Fig.
20
6. After the system is nearly dis-
charged, open the high pressure
gauge valve very slowly to avoid
loosing an excessive amount of re-
frigerant
oil and allow any refrigerant
remaining in the compressor and
high pressure line to discharge.
EVACUATING THE SYSTEM
1.
Discharge the system as de-
scribed in the foregoing procedure.
2. Attach a •tank of Refrigerant-12
and a vacuum pump to the manifold
gauge set. Make certain the Refriger-
ant-12 tank valve is tightly closed.
3. Open both manifold gauge set
valves.
4. Run the vacuum pump until
the low pressure gauge reads at least
25
inches and as close to 30 inches
of vacuum as possible
.
Continue
vacuum pump operation for 20-30
minutes to remove any moisture out
of the system. Turn off the pump
and close both gauge valves.
CHARGING THE SYSTEM
1.
Discharge and evacuate the
system as outlined in the foregoing
procedures.
2. Leave the vacuum pump valve
closed
.
3. Set the low pressure (suction)
manifold gauge valve at the full
counter-clockwise or open position.
4. Set the high pressure (dis-
charge) manifold gauge valve at the
full
clockwi~e
or closed position.
5. Open the Refrigerant-12 tank
valve to allow refrigerant to enter
the system, and observe the gauges.
When both gauges reach 60 to 80
pounds at approximately 75 degrees
F, shut off the tank valve.
6. Perform the leak test with the
leak detector (Fig. 21
).
7. Set the A/C controls for max-
imum cooling (Fig. 5).
8. Start the engine and open the
R-12 tank valve again to prevent
drawing vacuum on the suction side.
9. With the engine running at
1500 rpm, complete charging the
system until the specified weight of
refrigerant has
entered
the
system.
The sight glass should be clear with
no bubbles visible at this time. (Note:
Under 70 degrees F ambient a few
bubbles may appear in the sight glass).
10. If the refrigerant will not enter
the systein due to low temperature,
it may be necessary to place the
~efrigerant-12
tank in a container of
hot water at about 150 degrees F.
This will increase the R -12 pressure
and force the gas from the tank
during
charging.
Never heat the Re-
VALVE
CLOSED
L 1672-B
FIG. 18
frigerant-12 tank with a torch. A
dangerous explosion may result.
11. During the charging, the high
pressure (discharge) side may build
up to an excessive value. This can
be caused by an overcharge of refrig-
erant, or an overheated engine, in
combination with high surrounding
temperatures. Never allow the high
pressure
to
exceed 240 pounds while
charging.
If it does, stop the engine,
determine the
cause,
and correct it.
12. After the proper charge has
been made, close the Refrigerant-12
tank valve, and check the system
pressures for proper operation. (Low
pressure suction gauge 4-25 psi; high
pressure discharge gauge 120-170 psi
at 70 to 90 degrees F ambient).
13.
After satisfactory operation has
been achieved, disconnect the mani-
fold gauge set high and low pressure
hoses from the service valves
(Fig.
20).
14. Install caps on the service
valves and the manifold gauge set
lines (Fig. 18).
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