TM 9-4120-357-14
5-12. Brazing/Soldering Tubing Connections.
Most of the tubing connections to fittings and components are soldered or brazed to provide mechanical strength and to
ensure complete freedom from leaks under pressure.
To achieve trouble-free leak--tight tubing connections, the fol-
lowing practices are recommended.
a. Clean solder or filler material from tubing ends that have been debrazed, in the following manner:
(2) Wearing welder's gloves, heat the tubing end evenly all around to the melting point of the filler material.
(3) Grasp the fiberglass cloth firmly in the gloved hand, and pull it over the tubing end with a twisting -motion.
b. Form wires, capillary tubes or other parts subject to heat damage away from the brazing area, or protect them
with a sheet-metal shield.
c. To prevent melting connections adjacent to the one being crazed, use a hot enough flame to achieve the melt-
ing point quickly, and move the flame around all sides of the joint.
d. When brazing expansion valves or other components that can be warped or damaged by excessive heat, wrap
all parts except the joint to be brazed in wet cloth.
e. Always provide a flow of dry nitrogen through the tubing and joint where brazing, to prevent internal oxidation
and scaling.
WARNING
Never heat tubing or components in which there is refrigerant gas.
The gas decomposes at high temperatures to form carbonyl chlo-
ride (phosgene) which is toxic and corrosive.
5-13. Pressure Testing.
Pressure-Testing the refrigeration system is an important diagnostic procedure which you should perform whenever the
system has been newly recharged after replacement of a component, or when the air conditioner is operating ineffi-
ciently. Pressure testing is accomplished by connecting pressure gages to the gage ports of the suction line and dis-
charge line service valves, operating the refrigeration compressor, and determining that pressures are within normal
ranges for the temperatures encountered. Proceed as follows:
a. Access to Service Valves. Unscrew four panel fastener screws which secure the front access panel to the
lower part of the air conditioner. Remove the panel. The service valves are located as shown in Figure 1-2.
b. Installation of Instruments. Unscrew caps from gage ports of service valves, and connect a set of bourdon-
type refrigeration pressure gages to the gage ports. Install the front access panel, and route the gage lines through the
circuit breaker reset opening. Close the opening with the plastic sheet and tape to ensure normal air circulation through
the condenser coil. Position an accurate thermometer in the return air intake to the evaporator fan section, and another
in the air intake to the condenser for indicating the ambient temperature. The condenser thermometer should not be ex-
posed to direct sunlight when the reading is made. If necessary, provide a space heater to obtain an adequate supply of
warm return air to the unit.
c. Performing the Test.
(1) Turn the selector switch to cool, and the temperature control thermostat to maximum decrease.
(2) Slowly open the suction line and discharge line service valves to which pressure gages have been at-
tached.
(3) Record the temperatures indicated by both thermometers, and the pressures indicated by both pressure
gages. Compare the readings with the normal ranges indicated in the following table:
5-12
