EXPANSION VALVE INSPECTION, TEST AND ADJUSTMENT (Continued)

TM 5-4120-359-14

(2) Loosen the screws and nuts in the bulb straps that attach the sensing bulb to the suction line, and pull the

bulb out of the straps. Take care to note the position (center top of suction line) of the bulb.

CAUTION

Use care to not damage or kink the capillary.

(3) Connect a remote control module and a power cable to the air conditioner.

WARNING

The following test must be conducted with the power on. Exercise extreme caution.

(4) Turn on power to air conditioner.

(5) Place the sensing bulb in a container of ice water or crushed ice so that it is reduced to a temperature near

32F (0C).

(6) Set the temperature thermostat control knob fully counterclockwise to COOLER position, place one hand on

the exposed suction line, and start the air conditioner in COOL mode. If a drop in temperature is felt on the suction return

line, the expansion valve is not closing fully and should be adjusted or replaced.

CAUTION

When performing the next test, turn the air conditioner to OFF as soon as a definite

drop in temperature is felt on the suction return line. If the test conditions are

continued more than a few seconds, the expansion valve will fully open and an

excessive flood-back of liquid refrigerant may damage or destroy the compressor.

(7) With one hand still on the suction return line, remove the sensing bulb from the container and warm it in the

other palm. If a temperature drop is not felt in the suction return line by the time the sensing bulb no longer feels cold to

the hand, the expansion valve is not opening and should be adjusted or replaced. As soon as a temperature drop is felt,

turn the air conditioner to OFF.

d. Adjustment. The expansion valve, as supplied with the unit, is preset at the factory. This valve should not be

adjusted unnecessarily. When adjustment is necessary, see the following instructions:

(1) Remove insulation from a spot on the suction line near the sensing bulb of the thermal expansion valve to be

adjusted.

(2) Install an accurate thermometer or the probe of a thermocouple on a bare spot, using a small amount of the

thermal mastic, if available, to improve conductivity. Tape the thermometer bulb or thermocouple junction in position, and

cover with insulating material.

(3) Connect LOW SIDE hose of charging manifold to unit LOW SIDE service valve.

(4) Check that manifold valves are closed.

(5) Loosen the hose connections at the charging manifold slightly.

(6) Slightly open the unit LOW SIDE service valve to allow a small amount of refrigerant to purge the hose.

Tighten the hose connection at the manifold.

(7) Fully open the LOW SIDE service valve.

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