SERVICE EVACUATION

TM 9-4120-425-14&P

REFRIGERATION SYSTEM SERVICING (EVACUATION) - Continued

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NOTE

In the event the compressor was replaced as a result of burn-out, check that

compressor burn-out procedures were followed. See WP 0076-00.

SERVICE EVACUATION

Connect the hose from the low pressure service valve to the compound gauge side of the charging manifold. The

hose from the high pressure service valve shall be connected to the high pressure gauge side of the charging

manifold.

Open both service valves.

Attach center hose assembly charging manifold to vacuum pump.

Start vacuum pump.

Open charging manifold valves.

Run the vacuum pump until approximately a 300 micron vacuum is reached.

NOTE

Inability to reach 300 microns may indicate either a leak or a problem with the pump.

Close manifold valves and check compound gauge. Record reading. Let unit sit for one hour. Observe compound

gauge reading.

If the system holds the vacuum without change of pressure, proceed to step 10.

If the vacuum cannot be held for one hour, one of the following reasons may account for the problem:

Presence of water vapor in the system. Continued pumping will correct this condition.

Leak in the refrigeration system. Break the vacuum with dry nitrogen and retest for leaks. See WP 0052-00.

Internal leakage of vacuum pump. Test the pump by connecting a vacuum gauge directly to the vacuum pump

intake and continue to pump. If pump still fails to reach approximately 300 microns, the pump is faulty.

10. Close charging manifold valves.

11. Stop vacuum pump.

12. Disconnect pump from center hose connection.

13. Charge system with refrigerant-22. See WP 0054-00.

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