A/C SYSTEM MAINTENANCE - CONTINUED
EVACUATION - CONTINUED
Ensure manifold gauge set (1) valves (2 and 3) are closed.
Disconnect charging hose (6) from recovery station inlet (7) on refrigerant service unit.
Check oil level in vacuum pump. Add oil as necessary. Refer to vacuum pump OEM manual for correct procedure.
Connect charging hose (6) to inlet (9) on vacuum pump.
Open both manifold gauge set (1) valves (2 and 3) completely. Turn valves counterclockwise to open.
Evacuate A/C system. Refer to vacuum pump OEM manual for operation instructions.
At high elevations, less vacuum is required. 28 inHg to 29 inHg (95 kPa to 98 kPa) is the required specifica-
tion at sea level. For every 1,000 ft (305 m) above sea level, decrease the required specification by 1 inHg (3
Vacuum Required to Boil Water
Ambient Temperature °F (°C)
in A/C System inHg (kPa)
28 inHg (95 kPa)
28.5 inHg (96.5 kPa)
28.8 inHg (97.5 kPa)
29.2 inHg (98.8 kPa)
Operate vacuum pump until low pressure gauge (10) indicates a vacuum between 28 inHg to 29 inHg (95 kPa to 98
After vacuum in A/C system reaches between 28 inHg to 29 inHg (95 kPa to 98 kPa), operate vacuum pump for a mini-
mum of 90 minutes.
The evacuating procedure removes air and moisture from the system. Do not use the vacuum pump prima-
rily to indicate a system leak.
If specific vacuum cannot be reached, A/C system may have a leak. Repair all leaks and repeat steps 1 through 8.
After 28 inHg to 29 inHg (95 kPa to 98 kPa) vacuum has been reached and held for an additional 90 minutes, close man-
ifold gauge set (1) valves (2 and 3) completely.
Turn OFF vacuum pump. Refer to vacuum pump OEM manual for operation instructions.