ADJUSTMENT - TM-5-4120-393-140250

TM 5-4120-393-14

5-19. Expansion Valve (Primary) (cont)

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

of the straps.

WARNING

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

Place the sensing bulb (3) in a container of ice water or crushed ice so that it is reduced to a temperature near 32 F

(0C).

Set the TEMPerature control thermostat knob fully DE CREASE (counterclockwise), place one hand on the exposed

suction return 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 replaced. if the return line temperature remains constant,

check the pressure gage; it should indicate approximately 58 2 psi (4.0 0.14kg/cm ). If the pressure is not within

the above limits, test the operation of the quench valve (see para 5-20) and the pressure regulator valve (see para 5-

24) before attempting adjustment of the evaporator expansion valve.

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.

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 replaced. As soon as a temperature drop is felt, turn the air

conditioner to OFF.

5-44