LG LMX28988 Series User manual

CAUTION
BEFORE SERVICING THE UNIT,
READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
MODEL : LMX28988**
LMX25988**
COLOR : STAINLESS(ST)
SMOOTH BLACK(SB)
SUPER WHITE(SW)
REFRIGERATOR
SERVICE MANUAL

- 2 -
CONTENTS
SAFETY PRECAUTIONS ....................................................................................................................................................... 2
1. SPECIFICATIONS .......................................................................................................................................................... 3-4
2. PARTS IDENTIFICATION ................................................................................................................................................. 5
3. DISASSEMBLY ............................................................................................................................................................ 6-16
REMOVING AND REPLACING REFRIGERATOR DOORS ............................................................................................. 6
DOOR ................................................................................................................................................................................ 7
DOOR ALIGNMENT .......................................................................................................................................................... 8
FAN AND FAN MOTOR(EVAPORATOR) ......................................................................................................................... 8
DEFROST CONTROL ASSEMBLY ................................................................................................................................... 8
LAMP ................................................................................................................................................................................. 9
MULTI DUCT ..................................................................................................................................................................... 9
MAIN PWB ....................................................................................................................................................................... 10
DISPENSER .................................................................................................................................................................... 10
DISPLAY PCB ................................................................................................................................................................. 10
ICE BUTTON ASSEMBLY ............................................................................................................................................... 10
WATER BUTTON ASSMEBLY ........................................................................................................................................ 11
ICE CORNER DOOR REPLACEMENT ........................................................................................................................... 11
ICEMAKER REPLACEMENT ..................................................................................................................................... 11-12
SUB PWB FOR WORKING DISPENSER ....................................................................................................................... 12
CAP DUCT MOTOR REPLACEMENT ............................................................................................................................ 12
HOW TO REMOVE A ICE BIN ........................................................................................................................................ 13
HOW TO INSERT A ICE BIN ........................................................................................................................................... 13
HOW TO REMOVE AND REINSTALL THE PULLOUT DRAWER ............................................................................. 14-15
WATER VALVE DISASSEMBLY METHOD .................................................................................................................... 16
FAN AND FAN MOTOR DISASSEMBLY METHOD ........................................................................................................ 16
TOP DRAWER ................................................................................................................................................................. 17
BOTTOM DRAWER ......................................................................................................................................................... 17
4. ADJUSTMENT ........................................................................................................................................................... 18-19
COMPRESSOR ................................................................................................................................................................ 18
INTRODUCTION OF E-LINEAR COMPRESSOR ...................................................................................................... 18-20
5. CIRCUIT DIAGRAM ................................................................................................................................................... 21-22
6. TROUBLESHOOTING .................................................................................................................................................... 23
7. PCB PICTURE ........................................................................................................................................................... 24-26
8. Troubleshooting With Error Display ....................................................................................................................... 27-35
9. Troubleshooting Without Error Display ................................................................................................................. 36-44
10. Reference .................................................................................................................................................................. 45-48
11. COMPONENT TESTING INFORMATION ................................................................................................................. 48-56
12. TROUBLESHOOTING .............................................................................................................................................. 57-63
13. ICEMAKER OPEARTING AND TROUBLE SHOOTING METHOD ......................................................................... 64-67
14. DESCRIPTION OF FUNCTION & CIRCUIT OF MICOM ........................................................................................... 68-71
SAFETY PRECAUTIONS
Please read the following instructions before servicing your refrigerator.
1. Unplug the power before handling any elctrical componets.
2. Check the rated current, voltage, and capacity.
3. Take caution not to get water near any electrical components.
4. Use exact replacement parts.
5. Remove any objects from the top prior to tilting the product.

1-1 LMX28988**
- 3 -
1. SPECIFICATIONS
DOOR DESIGN
DIMENSIONS (inches)
NET WEIGHT (pounds)
COOLING SYSTEM
TEMPERATURE CONTROL
DEFROSTING SYSTEM
DOOR FINISH
HANDLE TYPE
INNER CASE
INSULATION
ITEMS
Side Rounded
35 3/4 X 35 3/8 X 69 3/4 (WXDXH) 28cu.ft.
165 kg. (364 lb)
Fan Cooling
Micom Control
Full Automatic
Heater Defrost
PCM, VCM, Stainless
Bar
ABS Resin
Polyurethane Foam
SPECIFICATIONS
VEGETABLE TRAY
COMPRESSOR
EVAPORATOR
CONDENSER
REFRIGERANT
LUBRICATING OIL
DEFROSTING DEVICE
ITEMS
Clear Drawer Type
Linear
Fin Tube Type
Spiral Condenser
R-134a (145 g)
ISO10 (280 ml)
SHEATH HEATER
LED Module(24)
LED Module(24)
SPECIFICATIONS
LAMP REFRIGERATOR
FREEZER
DIMENSIONS
Depth w/ Handles
Depth w/o Handles
Depth w/o Door
Depth (Total with Door Open)
Height to Top of Case
Height to Top of Door Hinge
Width
Width (door open 90 deg. w/o handle)
Width (door open 90 deg. w/ handle)
A
B
C
D
E
F
G
H
I
35 3/8 in
32 7/8 in
29 in
47 5/8 in
68 3/8 in
69 3/4 in
35 3/4 in
39 1/4 in
44 1/4 in
Description LMX28988**
●28 cu.ft.

- 4 -
1-2 LMX25988**
DOOR DESIGN
DIMENSIONS (inches)
NET WEIGHT (pounds)
COOLING SYSTEM
TEMPERATURE CONTROL
DEFROSTING SYSTEM
DOOR FINISH
HANDLE TYPE
INNER CASE
INSULATION
ITEMS
Side Rounded
32 23/32 X 35 3/8 X 69 3/4 (WXDXH) 25cu.ft.
153kg (337lb)
Fan Cooling
Micom Control
Full Automatic
Heater Defrost
PCM, VCM, Stainless
Bar
ABS Resin
Polyurethane Foam
SPECIFICATIONS
VEGETABLE TRAY
COMPRESSOR
EVAPORATOR
CONDENSER
REFRIGERANT
LUBRICATING OIL
DEFROSTING DEVICE
ITEMS
Clear Drawer Type
Linear
Fin Tube Type
Spiral Condenser
R-134a (130 g)
ISO10 (280 ml)
SHEATH HEATER
LED Module(18)
LED Module(12)
SPECIFICATIONS
LAMP REFRIGERATOR
FREEZER
DIMENSIONS
Depth w/ Handles
Depth w/o Handles
Depth w/o Door
Depth (Total with Door Open)
Height to Top of Case
Height to Top of Door Hinge
Width
Width (door open 90 deg. w/o handle)
Width (door open 90 deg. w/ handle)
A
B
C
D
E
F
G
H
I
35 3/8 in
32 7/8 in
29 in
46 3/64 in
68 3/8 in
69 3/4 in
32 23/32 in
36 7/32 in
41 7/32 in
Description LMX25988**
●25 cu.ft.

- 5 -
2. PARTS IDENTIFICATION
5
6
6
1
2
4
34
ADJUSTABLE REFRIGERATOR SHELVING
1
The refrigerator compartment shelves are adjustable to
allow flexibility for storage needs.
GALLON STORAGE BINS
2
Three interchangeable bins can be arranged to suit your
storage needs.
REMOVABLE ICE STORAGE BIN
3
The ice storage bin can be removed to fill ice buckets,
coolers, or pitchers.
LED INTERIOR LAMPS
4
Two separate LED arrays light the freezer and
refrigerator interiors.
CAN STORAGE BIN
5
FIXED DOOR BINS
6

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3. DISASSEMBLY
3-1 REMOVING AND REPLACING REFRIGERATOR DOORS
●Removing Refrigerator Door
CAUTION: Before you begin, unplug the refrigerator. Remove food and bins from doors.
▶Left Door -FIG. 2
1. Disconnect water supply tube by pushing back on the disconnect ring (3).-FIG. 1
2. Open door. Loosen top hinge cover screw (1).
Use flat tip screwdriver to pry back hooks on front underside of cover (2). Lift up cover.
3. Disconnect door switch wire harness and remove the cover.
4. Pull out the tube.
5. Disconnect all 3 wiring harnesses (4). Remove the grounding screw (5).
6. Rotate hinge lever (6) counterclockwise. Lift top hinge (7) free of hinge lever latch (8).
7. Lift door from middle hinge pin and remove door.
8. Place the door with the insides facing up, on a not scratch surface.
CAUTION: When lifting hinge free from the latch, be careful that door does not fall forward.
▶Right Door -FIG. 3
1. Open the door, remove 1 screw on the top of the hinge cover. Loosen top hinge cover screw (1). Lift up cover (2).
2. Disconnect door switch wire harness and remove the cover.
3. Rotate hinge lever (3) clockwise. Lift top hinge (4) free of hinge lever latch (5).
4. Lift door from middle hinge pin and remove door.
5. Place the door with the insides facing up, on a not scratch surface.
CAUTION: When lifting hinge free from the latch, be careful that the door does not fall forward.
Correct Incorrect
Figure 2 Figure 3
Figure 1
1) Insert the tube until you can see only one of
the lines printed on the tube.
2) After inserting, pull the tube to ascertain that
it is secure.
3) Assemble clip.

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1. Remove gasket
Pull gasket free from gasket channel on the four
remaining sides of door.
3-2 DOOR
●Mullion Removal
1. Remove 2 screws.
●Door Gasket Removal
2. Lift Mullion up carefully.
3. Disconnect wire harness.
●Door Gasket Replacement
1. Insert gasket into channel
Press gasket into channels on the four remaining
sides of door.
2. Insert mullion into the channel.
Insert the cover assembly into bracket, door.
●Mullion Replacement
1. Connect wire harness.
3. Assemble 2 screws.

- 8 -
*Ice Fan Scroll Assembly Replacement
1) Remove the plastic guide on the left side, using a
phillips screwdriver to remove the screws.
2) Pull off the sensor cover.
3) Remove the grill cover.
4) Gently pull on the grill assembly to remove.
5) Disconnect the wiring harness.
6) Remove all screws on the scroll assembly.
(1) (2)
(3) (4)
(5) (6)
3-5 DEFROST CONTROL ASSEMBLY
Defrost Control assembly consists of Defrost Sensor and
FUSE-M.
The Defrost Sensor works to defrost automatically. It is
attached to the metal side of the Evaporator and senses its
temperature. At 46F(8°C), it turns the Defrost Heater off.
Fuse-M is a safety device for preventing over-heating of
the Heater when defrosting.
1. Pull out the grille assembly. (Figure 1)
2. Separate the connector with the Defrost Control
assembly and replace the Defrost Control assembly after
cutting the Tie Wrap. (Figure 2)
Figure 1 Figure 2
GRILLE ASSEMBLY DEFROST-CONTROL
ASSEMBLY
3-3 Door Alignment
If the space between the door are uneven,
follow the instructions to align them.
Remove the Base Grillie. Turn the leveling legs counter
clock wise to raise or clock wise to lower the height of the
front of the refrigerator by using flat blade screw driver or
11/32" wrench. Use the wrench (Included with the User
Manual) to adjust the bolt in the door hinge to adjust the
height. (CCW to raise or CW to lower the height.)
3-4 FAN AND FAN MOTOR(EVAPORATOR)
1. Remove the freezer drawer. (If your refrigerator has an
icemaker, remove the icemaker first)
2. Remove the plastic guide for slides on left side by
unscrewing phillips head screws.
3. Remove the grille by removing 4 screws and pulling the
grille forward.
4. Remove the Fan Motor assembly by loosening 3 screws
and disassembling the shroud.
5. Pull out the fan and separate the Fan Motor and Bracket.
FAN MOTOR
BRACKET
MOTOR
Shroud

- 9 -
1. Unplug refrigerator power cord form outlet.
2. Remove screw with driver.
3. Grasp the cover Lamp, pull the cover downward.
3-6-2 Freezer Compartment Lamp
3-7 MULTI DUCT
1. Romove the upper and
lower caps with a flat
screwdriver and remove
2 screws.
(Figure 3)
2. Disconnect the lead wire
on the bottom position.
Figure 3
3-6 LAMP
Unplug, or disconnect power at the circuit breaker.
If necessary, remove top shelf or shelves.
1) Release 2 screws.
2) Hold both ends and pull down to remove.
3-6-1 Refrigerator Compartment Lamp
4) Use a flat tool as shown below to remove the lamp
cover.
5) To remove the LED assembly, pull apart the cover.
Cover, lamp
Case, lamp
LED, Assembly
3) To remove the lamp case and cover, release 2 screws
as shown.

- 10 -
3-8 MAIN PWB
1) Loosen 3 screws on the PWB cover.
3-9 DISPENSER
1) Pull out the drain 2) Use these 2 holes to pull
out the bottom
4) Holding the inner side of
the dispenser pull
forward to remove.
2) Remove the PWB cover
3) Disconnect wire harness and replace the main PWB in
the reverse order of removal.
3-10 DISPLAY PCB
As shown below, remove 1 screw on the PCB fixing screw.
Remove the display PCB fixing screw.
3-11 ICE BUTTON ASSEMBLY
1) Remove the 1 screw holding the lever.
2) Remove the spring from the hook.
3) Push and pull on the tab to remove.
CAUTION: When replacing the dispenser cover make
sure the lead wire does NOT come off and the water line
is not pinched by the dispenser.
Button Lever
Case, PCB Display PCB
5) Remove the
lead wire.
3) If nozzle is interfered with button, push and pull out the
bottom of button and then pull out the right side.

- 11 -- 11 -
3-13 ICE CORNER DOOR REPLACEMENT
1) Loosen the front screw as shown in the picture.
2) Lift up the hinge with one hand.
3) Pull out the Ice Corner Door with the other hand.
3-12 WATER BUTTON ASSMEBLY
1) Remove screws.
2) Grasp the Button assembly and lift.
Button Lever
hinge
3-14 ICEMAKER REPLACEMENT
1) Remove 4 screws as shown.
2) Grasp the bottom of motor cover assembly and pull
slowly.
3) Disconnect wire harness from wall of compartment.
In-door
motor

- 12 -
3-16 CAP DUCT MOTOR REPLACEMENT
1) Separate the Housing of the Cap Duct Motor.
3) When replacing the motor, check the position of the door
duct and the link for proper fit.
Link
Duct Door
Cap Duct Motor
NG Position
2) Unscrew 3 screws to disassemble the motor.
4) Insert 2 screws.
5) Push housing aside.
3-15 SUB PWB FOR WORKING DISPENSER
1) Disconnect the wire harness.
2) Remove 1 screw from PWB and replace with new PWB.
CAUTION: Make sure that the motor housing is taped to
the mold, if not positioned correctly the cover will not fit
properly.

- 13 -
3-17 HOW TO REMOVE A ICE BIN
1) Grip the handles, as shown.
2) Tilt and lift slightly as shown.
3-18 HOW TO INSERT A ICE BIN
1) Insert the Ice Bin, slightly tilting to avoid touching the
Icemaker. (Especially, Ice-Detecting Sensor)

3) Remove ice bin slowly.

- 14 -
3-19 HOW TO REMOVE AND REINSTALL THE PULLOUT DRAWER
3-19-1 Follow Steps to Remove
Step 1) Open the freezer door. Step 2) Remove the lower basket.
Step 3) Remove the two screws from the guide rails
(one from each side).
Step 4) Lift the freezer door up to unhook it from the rail
support and remove.
Pull both rails to full extension.
Step 5) First: Remove the gear from the left side first by releasing the tab behind the gear, place a screwdriver between the
gear and the tab and pull up on the gear.
Second: Remove the center rail.
Third: Remove the gear from the right side by following the same steps for the left side.
NOTE: THIS TAB MUST BE PUSHED IN TO RELEASE THE GEAR.
Pull the Tab from the Motor.

- 15 -
3-19-2 Follow Steps to Reinstall
Step 1) Reinstall the right side gear into the clip.
Step 2) Insert the rail into the right side gear. Gears do not
need to be perpendicular to each other.
Step 3) Insert the rail into the left side gear, and insert the
gear into the clip.
Step 4) The rail system will align itself by pushing the rails
all the way into the freezer section.
Pull the rails back out to full extension.
Step 5) Reinstall the freezer door by inserting the rail tabs
into the guide rail.
Step 6) Reinstall the two screws into the guide rails
(one from each side).
Step 7) Reinstall the lower basket, and close the freezer
door.

- 16 -
3-20 WATER VALVE DISASSEMBLY METHOD
1) Turn off the water to unit. Remove the waterline from the
valve.
3-21 FAN AND FAN MOTOR DISASSEMBLY
METHOD
1) Remove screws for the Drain Pipe Assembly and the 1
connected to the Motor Cover.
2) Remove cover and 1 screw from the valve.
3) Separate the housing and remove the valve.
4) Remove the clip, and press the collet to separate the
tube from the connector. Note: there maybe some water
in the line.
Mechanical Cover
Housing
MOTOR COVER
2) Separate the Fan Assembly and Motor, turn counter
clockwise to remove from the motor shaft.
FAN ASSEMBLY MOTOR
Assemble in reverse order. Taking care to avoid.
1. Do not to bend the tube during assembly.
2. Press the Water Dispenser button letting water pour out,
this checks for any leaks in the tube connection, this may
vary depending on the water pressure
( about 2 minutes.).
Figure 59
Figure 60
Figure 61
Figure 62
Figure 63
Figure 64

- 17 -
3-22 TOP DRAWER
To remove the freezer drawer, pull the drawer open to full extension. Remove the drawer and Ice Bin lifting the basket from
the rail system.
To remove the freezer drawer, pull the drawer open to full extension. Remove the drawer and Ice Bin lifting the basket from
the rail system.
3-23 BOTTOM DRAWER
To remove the freezer drawer, pull the drawer open to full extension. Remove the lower DuraBase ®basket by lifting the
basket from the rail system.

- 18 -
4. ADJUSTMENT
4-2 INTRODUCTION OF E-LINEAR COMRESSOR
E-Linear compressor is run by mechanical part design
through automatically varying the cooling power. The
main parts consist of compressor and Sub PCB which
controls the compressor. PCB authorizes constant
voltage and constant frequency to the compressor and
protects it.
Drive half stroke after turning on initial power for 30
seconds. Then, slowly increase stroke and reach target
input. Once reaching the target input, input naturally
changes according to refrigerator load without any special
control.
Interval 1) Half stroke interval - after initial running, stay at
the initial value for 30 seconds
Interval 2) Running interval - Increase at every 0.8 till it
reaches the target input; it takes about 3’ 45”
Interval 3) CVCF interval - Run by target voltage and main
operating frequency and the input naturally
changes according to refrigerator load
❸
❶❷
4-1-1 Role
4-1 COMPRESSOR
The compressor intakes low temperature and low pressure
gas from the evaporator of the refrigerator and compresses
this gas to high-temperature and high-pressure gas. It then
delivers the gas to the condenser.
4-1-2 Note for Usage
(1) Be careful not to allow over-voltage and over-current.
(2) Do not drop or handle carelessly.
(3) Keep away from any liquid.
If liquid such as oil or water enters the Cover PTC
Compressor may fail due to breakdown of their
insulating capabilities.
(4) Always use the Parts designed for the compressor and
make sure it is properly attached to the compressor.
Parts may appear physically identical but could have
different electrical ratings. Replace parts by part number
and model number. Use only approved substitute parts.
4-1-3 Remove the cover PTC
(1) Remove the Cover Back M/C
(2) Loosen two screws on comp base
(3) Use a L-shaped flap tooll to pry off the cover
(4) Assembly in reverse order of disassembly
4-2-1 Control of Compressor Block Diagram
4-2-2 Compressor operating pattern
Compressor Controller Inverter
PWM
Signal
Frequ
-ency
Linear
Comp
DC link
Voltage
Main
Micom
Calculate counter
electromotive force
Counter elec-
tromotive force
Vcap Voltage
Control Block Diagram of Compressor
Comp. input

- 19 -
Multi-tester
4-2-4 Compressor problems diagnosis
When there is a problem or failure with the `operation,
you are kindly recommended to check it as follows ;
Measure the resistance between poles of the hermetic
terminal (as shown picture) with a multi-tester.
(measurement several minutes after power off)
Normal resistance range (measured at ambient
temperature 23℃)
Case 1-1
If the measured values lie in the normal resistance range as
in the table below,
Compressor is normal.
Case 1-2
If the measured values are above several MΩor a infinity,
Wire is disconnected in the shell.
Case 1-3
If the measured values are excessively of small number,
There is short somewhere in the shell.
1) Check to normality by measurement of resistance
According to ambient temperature or operation situation,
the values could show a little deviation.
4-2-3 Compressor protection logic
Since linear Comp conducts linear reciprocating motion,
we have protection logic for compressor, motor and PCB
as the below.
-Stroke Trip
During the operation, if stroke is above the target value,
decrease the target volt by 3V.
-Current Trip
Current trip is set in order to protect compressor
mechanical part and drive from the overcurrent that might
arise during the operation.
Check the current for every 416.7us and if the Trip
exceeds 1.86Arms more than three times at Comp ON,
forcibly stop and restart six minutes later.
-Lock Piston Trip
If stroke is under 5mm even if the current is more than
14Arms, Take it as ‘piston lock’ and restart after 2’30” of
Comp OFF. Check the current and stroke for every
416.7us and if the condition fits more than three times at
Comp ON, the Trip occurs.
-IPM fault Trip
It occurs if FO signal received from IPM is LOW. For
every 416.7us, check whether FO signal is LOW. The trip
occurs if it is found three times during the five
periods(83ms).
P : Power Line
C : Common Line
Resistance
6~8 Ω FC75LANE

- 20 -
Measure the resistance between pin of the connector (as
shown picture) with a multi-tester.
Standard for normality
-In order to decide whether compressor operating is normal
or not, check the output transfer during the refrigerator
operation.
-After input the initial power and compressor operates, wait
for 10 minutes to estimate.
-Compressor operation may be diagnosed as normal if the
voltage falls between 145V and 180V.
Warning
1. Please be cautious of electric shock and short (it is
estimated after turning on initial power).
2. If the voltage is estimated less than 80V, it is diagnosed
as bad.
2) Check to normality by measurement of Voltage
If compressor protection logic is running, LED Lamp’s
blinking frequency of sub PCB, which takes in charge of
control, can help estimate the protection logic’s symptoms
and the cause of its problems.
Trip name
Stroke Trip
Current Trip
Lock Piston Trip
IPM fault trip
Led Times
2
6
5
7
Comp Off Time
1min
6min
2min 30sec
20sec
3) Check problems by LED On & Off Count _ (Sub PCB)
<Fig. 1> <Fig. 2>
-Current Trip PCB defects or Cycle clogging maybe the
causes. After estimating winding resistance, estimate
compressor operation voltage to check if there is any
problem and take actions to repair cycle at replacement of
compressor.
-Stroke Trip can occur when the surrounding
temperature is high, C-Fan, F-Fan and so on are
constrained, or when cycle problems, such as moisture
blocking or compressor defect, are related.
-Lock Piston Trip Since compressor itself can be a
potential cause of a defect, estimate the compressor
resistance value according to #1’s compressor winding
value estimation method and estimate the #2’s
compressor operation voltage to decide whether it is
defective or not
(Before replacement of compressor, replace PCB and
conduct the replacement of compressor during
compressor replacement)
-IPM fault Trip Replace sub PCB since there is high
chance that it is caused by sub PCB’s part defect.