REFRIGERANT PRESSURE CHECK

TM 5-4120-359-14

s. Run the air conditioner in COOL mode (with TEMPERATURE CONTROL in full COOLER position) for 15

minutes.

CAUTION

Do not skip the next step.

After 15 minutes, observe the sight glass on back of condenser section.

Green center means the refrigerant moisture content is acceptable.

Yellow center means there is too much moisture in the system. It must be discharged, evacuated and

charged again.

Milky white or bubbly liquid means the system has a low charge.

Clear bubble-free liquid around the center means the system is fully charged.

u. If charge is low, add gas refrigerant.

(1) Be sure that drum is switched to gas position. Open the drum valve and the air conditioner low pressure

service valve.

(2) Continue to charge until sight glass is clear and bubble-free.

(3) Close the refrigerant drum valve and the air conditioner low pressure service valve.

v. Check air conditioner for proper cooling. There should be at least a 20 5F temperature difference between

evaporator discharge air and the inlet air.

w. Turn the MODE SELECTOR SWITCH to OFF.

x. Close the high and low pressure air conditioner service valves, and remove the charging manifold hoses from the

air conditioner service valves.

4-11. REFRIGERANT PRESSURE CHECK

Except in cases where it is obvious that the refrigerant charge has been lost, the first step in troubleshooting problems in

the refrigeration system should be to check discharge and suction pressures under operating conditions. Check

pressures as follows:

a. Turn the MODE SELECTOR SWITCH to OFF.

b. Connect individual pressure gages, or a refrigeration servicing manifold and hoses to the high (discharge) and low

(suction) service valves.

Open the low (suction) and high (discharge) service valves.

d. Both gages should read the same. Check the reading with the appropriate column in Table 4-3. If the system is

even partially charged, the pressure should be approximately equal to that shown in the table for the appropriate ambient

temperature. If the pressure is considerably less than shown in the table, the system does not contain enough refrigerant

to continue the pressure check; go to leak testing.

e. Turn the MODE SELECTOR SWITCH to the COOL mode with the TEMPERATURE CONTROL in the full

COOLER setting for a few minutes.

With the unit operating, allow gages to stabilize. Take readings of the two gages.

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