General Repair Procedures

TM 5-4120-274-15

(b) Remove cap from suction tube charg-

5-20. General Repair Procedures

ing valve.

a. If the refrigerant system must be opened for

( c ) Connect hose from refrigeration

repair or replacement of parts, first discharge the

charging hookup loosely to suction tube charging

refrigerant from the system. Refer to paragraph

valve. Open refrigerant drum shutoff valve slight-

5-21b for instructions for discharging the system.

ly to purge hose. Tighten connection at charging

b. After discharging the system allow the tub-

valve. Open shutoff valve and backseat charging

ing to warm to the ambient temperature before

valve.

opening the system; this delay will help prevent

(d) Refrigerant drum must be in up-right

the formation of condensation on the inside wall

position to allow only gaseous refrigerant to enter

of the tubing. Plug or cap all openings as a part

system.

is removed to minimize the entry of dirt and

(e) Start unit.

moisture into the system.

(f) TO Speed up charging, set refrigerant

c. Use a silver solder on all soldered connec-

drum in warm water. Never use a heating torch

tions. Silver solder (or equivalent) with a 50 per-

for this purpose.

cent silver capacity and a melting point of ap-

(g) Observe sight glass (fig. 3-13) at

proximately 1300 degrees F. is recommended.

the time of charging, and even though flash gas

Continually pass dry nitrogen through the tubing

is apparent, shutoff refrigerant flow and observe

or connections being soldered to prevent forma-

sight glass for a period of 10 to 20 minutes. If

tion of harmful copper oxides.

at the end of this time period the sight glass is

not free from the flash gas, admit a small amount

5-21. Servicing the Refrigerant System

of charge and observe for the same time period.

Repeat this operation until sight glass is clear.

a. Testing Refrigerant System for Leaks. Re-

(h) Frontseat charging valves and close

fer to paragraph 3-45b, and test refrigerant sys-

refrigerant drum shutoff valve. Stop the unit and

tem for leaks.

disconnect manifold hoses from charging valves,

b. Releasing Refrigerant for Service. Release

install caps.

refrigerant slowly to a well vented atmosphere.

(2) Weight method. With this method you

Adjust the release so that a vaporized discharge

are charging the unit with liquid.

is made to avoid loss of refrigerant oil.

(a) Evacuate the system, paragraph 5-21.

c. Evacuating the Refrigerant System.

(b) Connect a bottle of refrigerant-22 to

(1) General. Opening the system to the

discharge high side access fitting, figure 3-6.

atmosphere will cause entry of air and moisture

(c) Weight refrigerant bottle.

into the system. After any servicing operation,

(d) Invent charging cylinder and open

when the system is opened, the entire system

valve on refrigerant bottle and allow refrigerant

should be evacuated before recharging with re-

frigerant.

to flow through system.

(e) Periodically weigh bottle until it is

(2) Evacuation.

(a) Connect hose assemblies of evacuation

lighter by amount needed in system, must be ex-

act amount.

gage manifold to discharge valve access fitting

and to the suction access fitting of unit, refer to

Caution: Total amount of charge must

figure 3-6.

be exactly 53 oz

(b) Connect vacuum pump to center hose

of gage manifold.

5-22. Wiring Harness and Wire Leads

crons.

a. General. The electrical circuits in the refrig-

(d) Break vacuum by admitting refriger-

eration unit are completed by individual wire

ant, paragraph 521d(1).

leads or by leads laced or enclosed to form a wir-

ing harness, When testing, repairing, or replacing

Caution: Do not use the compound

the individual wires or harnesses refer to the wir-

gage as an indicator for satisfactory vacuum

ing diagram (fig. 1-5).

pressure.

b. Inspection. Inspect the wiring insulation for

d. Charging the Refrigerant System. There are

cracks and frayed material. Pay particular atten-

two preferred methods used to charge the re-

tion to the wires passing through holes in the

frigerant system.

frame or over rough edges. If inspection reveals

a broken or cut wire, and the break in the wire is

(1) Sight glass method.

(a) Evacuate the system, paragraph 5-21.

exposed, the wire must be repaired (d below). If

5-4