Section VI. EXPANSION VALVES

TM 5-4120-274-15

Section VI. EXPANSION VALVES

superheat does not reach the required value when

6-12. Expansion Valves

adjusted, check for dirt or other restrictions in the

a. General. Each air conditioner contains two

liquid line or expansion valve.

expansion valves One controls the refrigerant

d. Installation.

flow to the evaporator coil during the cooling cy-

(1) Refer to figures 3-10 and 3-11 and in-

cle. The other functions when the refrigerant

stall the expansion valve.

flows through the bypass cycle.

(2) Charge unit, refer to paragraph 5-21d.

b. Removal

(3) Replace cover panel refer to paragraph

(1) Remove cover panel, refer to paragraph

3-18.

(2) Discharge refrigerant from system, refer

6-13. Access Fittings

to paragraph 5-21c.

a. General. The access fittings provide access

(3) Refer to figures 3-10 and 3-11 and re-

to the refrigerant system for service.

move expansion valves.

b. Removal.

c. Adjustment.

(1) Remove side cap from expansion valve

(1) Remove front access panel, refer to para-

graph 3-18.

base.

(2) Slowly discharge the refrigerant charge

Note. Make sure thermal bulb is securely fastened

from system (para 5-21b).

to suction line and the bulb is covered with rubber insula-

(3) Unscrew valve stem from inside access

tion.

valve.

(2) Turn stem clockwise for higher super-

c. Installation.

heat and counterclockwise for lower superheat.

(1) Install valve stem into access valve.

One full turn is equivalent to approximately 2F

(2) Recharge system, refer to paragraph 5-

superheat. A suction gas superheat of 5F to 10F

21d.

out of the evaporator coil is satisfactory. A super-

(3) Install front access panel refer to para-

heat of 10F to 20F when measuring the super-

graph 3-18.

heat at the thermal bulb is also satisfactory. If the

Section VIII. SIGHT GLASS

erant is indicated by flash gas in the sight glass.

6-14. Sight Glass

b. Removal. Slowly discharge the refrigerant

a. General. The sight glass indicates the refrig

charge from system (para 5-21b). Refer to figure

erant moisture content. When the indicator is

3-13 and remove sight glass.

green the refrigerant is dry. A color shading into

c. Installation. Refer to figure 3-13 and install

yellow indicates that the refrigerant has become

sight glass.

contaminated with moisture. A shortage of refrig-

Section IX. FILTER DRIER

b. Removal. Slowly discharge the refrigerant

6-15. Filter Drier

charge from the system (para 5-21b). Refer to

a. General. The filter drier prevents the accu-

figure 3-6 and remove the filter drier.

mulation of moisture and contaminants within the

refrigeration system. The filter drier must be re-

c. lnstallation. Refer to figure 3-6 and install

placed each time the system is exposed to the at-

filter drier.

mosphere.

6-3