Frigidaire LGUB2642LF2, Service Manual

Page: 152 / 187

Sealed System
7-8
Low/High Side Leak or
Undercharge
A loss of refrigerant can result in any of the
following:
1. Excessive or continuous compressor operation.
2. Above normal freezer compartment temperature.
3. A partially frosted evaporator (depending on amount
of refrigerant loss).
4. Below normal freezer compartment temperature.
5. Low suction pressure (vacuum).
6. Low wattage.
The condenser will be “warm to cool”, depending on the
amount of refrigerant lost.
In the case of a low side refrigerant leak resulting in
complete loss of refrigerant, the compressor will run but
will not refrigerate. Suction pressure will drop below
atmospheric pressure and air and moisture will be drawn
into the system, saturating the filter drier. A system with
R-134a refrigerant and ester oil will become saturated
with moisture much faster than a system with R-12 and
mineral oil. Therefore, you must obtain a sample of the
oil and check with an oil test kit to determine the amount
of contamination. You will find that the oil in an R-134a
system will have to be replaced after most low side
leaks.
If there is reason to believe the system has operated for
a considerable length of time with no refrigerant and the
leak occurred in the low side of the system, excessive
amounts of moisture may have entered the system.
In such cases, the two stage service Dryer Filter part
number 5303918288 and vacuum procedure listed under
Refrigerant Leaks, need to be followed to prevent
repetitive service. Use caution to connect cap tubes
properly as described in the filter-drier replacement
section on page 7-16, otherwise the icemaker will not
work correctly.
If a slight undercharge of refrigerant is indicated and no
leak can be found after a thorough leak test, the charge
can be corrected without changing the compressor.
If a high side leak is located and some refrigerant
remains in the system it is not necessary to change the
compressor.
Testing for Refrigerant Leaks
If the system is diagnosed as short of refrigerant and
the system has not been recently opened, there is prob-
ably a leak in the system. Adding refrigerant without first
locating and repairing the leak or replacing the
component will not permanently correct the difficulty.
The leak must be found!
Sufficient refrigerant may have escaped to make it
impossible to leak test effectively. In such cases, add a
¼” line piercing valve to the compressor process tube.
Add sufficient refrigerant vapor to increase the pressure
to 75 lbs. per sq. in. Through this procedure, leaks are
more easily detected before discharging the system into
reprocess/recapture equipment. Check the low side for
leaks. Run the compressor 2 or 3 minutes and check
the high side for leaks. Recover refrigerant using an
EPA approved recovery system.
Checking For Internal Leaks
Before checking for internal leaks, check all accessible
system components and joints for leaks.
If an internal leak is suspected, it must be confirmed.
Use the following procedure:
1. Discharge the system by using refrigerant recovery
equipment.
2. Disconnect the condenser and the drier from the hot
tube on refrigerators. On food freezers, separate the
high and low pressure sides of the system. Pinch off
and solder closed one end of the part of the system
to be tested.
3. Solder a 1/4” charging hose fitting to the open end of
the part of the system to be tested.
4. Connect a pressure gauge and access valve to the
open end of the part of the system to be tested.
Pressurize to 250 lbs. using dry nitrogen or carbon
dioxide.
5. Leave the pressure on the hot tube for 24 hours.
Any drop in pressure is an indication of a leak.
The line piercing valve (clamp-on type) should be
used for test purposes only. It must be removed
from system after it has served its purpose.