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TM5-4120-377-14
e. Reassembly. If tubing sections or fittings were removed with a component, debraze them from the
component, clean the joints, and braze them to the new component before reinstallation.
f. Brazing. Braze joints within the air conditioner as follows:
(1) Position the component to be installed.
(2) To prepare a joint on a valve for brazing, disassemble the valve to the extent possible. Then wrap all
but the joint with a wet rag to act as a heat sink.
(3) Protect insulation, wiring harnesses, and surrounding components with appropriate shields.
(4) Be sure the work area is well ventilated and that dry nitrogen is flowing through the refrigeration
system at a rate of less than 1 -2 cfm (0.028-0.057 m3/minute).
(5) Apply sufficient heat uniformly around the joint to quickly raise it to a temperature that will melt the
filler alloy. Remove heat as soon as brazing is completed.
5-9.
LEAK TESTING THE REFRIGERANT SYSTEM
Supplies: Nitrogen cylinder (item 4, Appendix E)
Refrigerant 22 (item 10, Appendix E)
a. The entire repaired area should be thoroughly leak tested after repair or replacement of any component,
before it is recharged with refrigerant-22. Leak testing is also the method for troubleshooting when a system
has lost all or part of its refrigerant charge through an undetermined cause.
b. Testing Method. There are two acceptable methods for leak testing the refrigeration system.
(1) Refrigerant gas leak detector. If an electronic refrigerant gas leak detector is available it should be
used in accordance with the procedures contained in TM 9-4940-435-14, “Leak Detector, Refrigerant Gas.”
NOTE
The electronic refrigerant gas leak detector is highly sensitive to the presence of a minute
quantity of gas in the air, and due to this factor is quite effective in the detection of small
leaks. However, due to the rapid dispersion of refrigerant gas into the surrounding air,
difficulty may be encountered in pinpointing large leaks. The detector must be used in a
well ventilated but draft-free area.
(2) Soap solutions. In this method, a strong solution of a liquid detergent and water is brushed onto all
points of possible leakage while closely watching for the formation of bubbles.
If the soap solution testing method is used, thoroughly rinse with fresh water after testing
is completed. A residual soap film will attract and accumulate an excessive amount of
dust and dirt during operation.
c. Testing procedures. To perform leak testing by use of the electronic detector, it is necessary that the
system be pressurized with a proportion of refrigerant gas. To perform leak testing by use of the soap solution
method, the system may be pressurized with dry nitrogen alone.
(1) To pressurize a system that has some refrigerant charge, for either leak testing method:
(a) Remove the hose connection protective caps from the high and low pressure service valves.
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