TM 5-3805-296-23-4
0248
EVACUATION CONTINUED
NOTE
Less vacuum is required at high elevations. At sea level, 28 to 29 inHg (95 to 98 kPa) of
vacuum is required. For every 1,000 ft (305 m) above sea level, the required specification
decreases by 1 inHg (3 kPa).
AMBIENT
VACUUM REQUIRED TO BOIL WATER
TEMPERATURE
IN A/C SYSTEM
100F (38C)
28 inHg (95 kPa)
90F (32C)
28.5 inHg (96.5 kPa)
81F (27C)
28.8 inHg (97.5 kPa)
70F (21C)
29.2 inHg (98.8 kPa)
NOTE
Evacuation procedure removes air and moisture from A/C system. Do not use evacuation
procedure primarily to detect an A/C system leak.
4. Evacuate A/C system until low-pressure gauge indicates a vacuum of 28 to 29 inHg (95 to 98 kPa).
a. If specific vacuum cannot be reached, the A/C system may have a leak. Detect and repair all leaks and
repeat steps 1 through 4.
b. If specific vacuum can be reached, continue to evacuate A/C system for at least 30 minutes, and then
proceed to step 5.
NOTE
Excessive vacuum loss indicates a possible leak in A/C system.
Amount of vacuum loss in 5 minutes must not exceed 2 inHg (7 kPa).
5. If vacuum loss exceeds 2 inHg (7 kPa) in 5 minutes, repair all leaks and repeat steps 1 through 5. If vacuum
loss does not exceed 2 inHg (7 kPa) in 5 minutes, A/C system is ready to charge.
END OF TASK
0248-6