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PRECAUTIONS HA-9 < PRECAUTION > C D E F G H J K L M A B HA N O P The oil contained inside the vacuum pump is not compatible with the specified oil for HFC-134a (R-134a) A/C systems. The vent side of the vacuum pump is exposed to atmospheric pressure so the vac- uum pump oil may migrate out of the pump into the service hose. This is possible when the pump is switched off after evacuation (vac- uuming) and hose is connected to it. To prevent this migration, use a manual valve situated near the hose-to-pump connection, as follows. • Usually vacuum pumps have a manual isolator valve as part of the pump. Close this valve to isolate the service hose from the pump. • For pumps without an isolator, use a hose equipped with a manual shut-off valve near the pump end. Close the valve to isolate the hose from the pump. • If the hose has an automatic shut off valve, disconnect the hose from the pump: as long as the hose is connected, the valve is open and lubricating oil may migrate. Some one-way valves open when vacuum is applied and close under a no vacuum condition. Such valves may restrict the pump's ability to pull a deep vacuum and are not recommended. MANIFOLD GAUGE SET Be certain that the gauge face indicates HFC-134a (R-134a or 134a). Make sure the gauge set has 1/2 ″-16 ACME threaded con- nections for service hoses. Confirm the set has been used only with refrigerant HFC-134a (R-134a) along with specified oil. SERVICE HOSES Be certain that the service hoses display the markings described (colored hose with black stripe). All hoses must include positive shut- off devices (either manual or automatic) near the end of the hoses opposite the manifold gauge. SERVICE COUPLERS RHA270D SHA533D RHA272D |