Electric Heater Thermostat

TM 5-4120-273-15

with a reddish tip; or the flame may be entirely

extinguished.

(2) Soap solution method. Operate the air

conditioner (para 2-12). Brush all points of possi-

ble leakage with soap solution. Watch for bubbles.

Follow a definite sequence so that all joints will

be thoroughly tested. Wipe the solution from all

joints and mark any spot where leakage occurs.

3-46. Liquid Line Solenoid Valve

a. General. The liquid line solenoid valve (fig.

3-6) is automatically actuated by the thermostat

and controls the flow of refrigerant to the evapo-

rator coil.

b. Inspection. Inspect for cracked or broken

casing and damaged or broken terminals.

c. Testing. Test for continuity across coil with

multimeter set on OHMS. Refer to wiring diagram

(fig. 1-5) to establish points of continuity.

NOTE: TAG AND DISCONNECT

3-47. Equalizer Solenoid Valve

ELECTRICAL LEADS,

UNSOLDER AND DISCONNECT

a. General. The equalizer solenoid valve is ac-

TUBING AS NECESSARY.

tuated by the ON/OFF switch and serves to equal-

ize system pressures during shutdown, figures

MEC 4120-273-15/3-15

3-11,3-12.

b. Inspection. Inspect for cracked or broken

Figure 3-15. Fan speed pressure switch, removal and

casing and damaged or broken terminals.

installation.

c. Testing. Test for continuity across coil with

multimeter set on OHMS. Refer to wiring diagram

3-44. Electric Heater Thermostat

(fig. 1-5) to establish points of continuity.

a. General. The electric heater thermostat (fig.

3-11) is a protective device which prevents the

3-48. Access Fittings

heater elements from overheating.

b. Removal. Refer to figures 3-11, 3-12 and re-

a. General. The two access fittings (suction line

move electrical heater thermostat.

and discharge line) provide access to the refriger-

c. Testing. Test for continuity with multimeter

ant system figure 3-6.

set on OHMS. Refer to wiring diagram figure 1-5

b. Inspection. Inspect for cracked casing or

to establish points of continuity.

damaged threads.

d. Installation. Refer to figures 3-11, 3-12 and

install electric heater thermostat.

3-49. Pressure Relief Valve

a. General. Pressure relief valve (fig 3-6) is

3-45. Refrigerant Piping

located on a tee just below the filter-drier. The

a. Inspection. Inspect refrigerant piping for

pressure relief valve protects the refrigerant sys-

kinking, holes and unsatisfactory welding.

tem from excessive pressure.

b. Testing.

b. Inspection. Inspect for cracked or broken

(1) Halide torch leak detector. The pre-

casing.

ferred method of field testing for leaks in the re-

frigeration system is by using a halide torch, Op-

3-50. Pressure Regulating Valve

crate the air conditioner (para 2-12) and pass the

The evaporator pressure regulating valve (figs.

exploring tube slowly over all sweat fittings,

mechanical couplings, and valves. If refrigerant is

3-11, 3-12) regulate refrigerant pressure in the

leaking from the system the flame of the torch will

evaporator to prevent coil freeze up. The valve is

change from blue to green when the leak is small.

preset to establish a minimum pressure in the

evaporator of 58 psig.

If the leak is large, the flame will be a deep blue

3-19