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TM 5-4120-287-15
(3) The exploring tube of this detector should be run over all sweat fittings, all mechanical couplings, and all valves.
All portions of the system under refrigerant pressure should be methodically checked with this device.
(4) Check the refrigerant charge level (para 2-9 c (1)).
(5) Install the housing panels (para 3-23 c, 3-27 c and 3-29 c).
7-7.
Discharging Refrigerant System
a.
Remove air conditioner right-side access panel assembly (para 3-29 a).
b.
Remove the air conditioner charge valve cap.
c.
Attach a hose to the charge valve outlet and place the other end of the hose into a 500 ml (milliliter) graduated
cylinder.
d.
Discharge refrigerant by opening charge valve.
NOTE
Bleed the refrigerant slowly to prevent blowing oil out of the motor compressor assembly.
e.
Remove hose from charge valve when refrigerant discharge ceases. Note the amount of oil collected in the 500 ml
graduated cylinder.
7-8.
Evacuating Refrigerant System
NOTE
Replace the filter-drier unit before evacuating and charging the refrigerant system.
a.
Connect charging apparatus evacuation and charge hose (fig. 7-1) to the charge valve. Connect the vacuum pump
power cord to a suitable electrical power source.
b.
Open the vacuum pump shut-off valve and the vacuum control valve. Check that the refrigerant control valve is
closed.
c.
Start the vacuum pump.
d.
Evacuate the refrigerant system to 29 1 inches of mercury on the vacuum gage for no less than 20 minutes; then
close the air conditioner charge valve.
e.
Close the vacuum pump shut-off valve and the vacuum control valve on the charging unit.
f.
Shut down the vacuum pump.
g.
Close the air conditioner charge valve.
h.
Disconnect the evacuation and charge hose from the air conditioner charge valve; and replace the valve cap.
i.
Disconnect the vacuum pump power cord.
j.
Install the air conditioner right-side panel assembly.
7-9.
Charging Refrigerant System
NOTE
Replace the filter-drier unit before charging refrigerant system.
a.
Discharge and evacuate the refrigerant system according to paragraphs 7-7 and 7-8.
b.
Connect the refrigerant supply hose to a refrigerant-12 bottle, and open the refrigerant control valve to evacuate the
refrigerant supply hose. Close the refrigerant control valve when system pressure returns to 29 1 inches of mercury
vacuum.
WARNING
Wear protective gloves and goggles when handling refrigerant-12 bottles.
c.
Release the scale beam lock to free the platform scale. Adjust zero set knob to obtain a zero scale reading.
d.
Invert the refrigerant-12 bottle, and place it on the platform scale. Record the weight of the refrigerant-12 bottle.
Note. The refrigeration system charges more rapidly when the refrigerant-12 bottle is placed in an inverted position. If
the refrigerant-12 has been stored in a cold area, the pressure within the cylinder may not be sufficient to charge the
system. Place the base of the refrigerant-12 bottle in a pail of warm water (approx. 120F.
WARNING
Do not heat the tank with an open flame or apply heat in excess of 125° F.
e.
Close the vacuum control valve.
f.
Shut down the vacuum pump.
g.
Open the refrigerant-12 bottle valve.
h.
Open the charging unit refrigerant control valve, and observe the scale. When the scale reading is 10.0 pounds less
than the reading recorded in d, above, close the refrigerant control valve.
CAUTION
The refrigerant charge is critical within 1 lb. of the required amount. Extreme care must be taken when
admitting refrigerant into the system since it is possible to admit large quantities of refrigerant in a very
short time. Weigh the refrigerant bottle at frequent intervals to determine when the correct amount of
refrigerant has been admitted into the system.
7-4
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