Whirlpool ATE0743SPP Technical Manual page 60

AN UNDERCHARGED SYSTEM
An undercharged system will result in poor
performance (low pressures) in both the heat-
ing and cooling cycle.
Whenever you service a unit with an under-
charge of refrigerant, you can usually suspect
a leak. The leak must be repaired before charg-
ing the unit.
To check for an undercharged system, turn the
unit on, and allow the compressor to run long
enough (15 to 20 minutes) to establish working
pressures in the system.
During the cooling cycle, listen carefully at the
exit of the capillary tube into the evaporator. An
undercharged system will cause an intermit-
tent "hissing" and "gurgling" sound. Intermit-
tent frosting and thawing of the evaporator is
another indication of a low charge. However,
frosting and thawing can also be caused by
insufficient air over the evaporator.
Check for an undercharged system at the
compressor. If the compressor seems quieter
than normal, it is an indication of a low refriger-
ant charge. A check of the amperage drawn by
the compressor motor should show a lower
reading (check the unit's specifications).
After the unit has run 10 to 15 minutes, check
the gauge pressures.
Gauges connected to an undercharged sys-
tem will have low head pressures, and sub-
stantially low suction pressures.
Undercharged System
6-2