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LG LRDC20731ST Service Manual
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LG LRDC20731ST Service Manual

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REFRIGERATOR
SERVICE MANUAL
CAUTION
BEFORE SERVICING THE UNIT,
READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
LRDN20720
**
LRDN20725
**
LRDN22711
**
LRDN22720
**
LRDN22725
**
LRDC20731
**
**
LRDC22731
**
LRDC22743
**

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Summary of Contents for LG LRDC20731ST

  • Page 1 REFRIGERATOR SERVICE MANUAL CAUTION BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL. LRDN20720 LRDN20725 LRDN22711 LRDN22720 LRDN22725 LRDC20731 LRDC22731 LRDC22743...

  • Page 2: Table Of Contents

    CONTENTS SAFETY PRECAUTIONS ............................... 2 SPECIFICATIONS................................... 3 PARTS IDENTIFICATION ............................... 4 DISASSEMBLY..................................5-6 DOOR....................................5 DOOR SWITCH..................................5 FAN AND FAN MOTOR................................ 6 DEFROST CONTROL ASSEMBLY............................6 LAMP....................................6 CONTROL BOX-REFRIGERATOR ............................6 MULTI DUCT ..................................6 ADJUSTMENT..................................7-8 COMPRESSOR..................................7 PTC-STARTER..................................

  • Page 3: Specifications

    1. SPECIFICATIONS 20 cu. ft. / 22 cu. ft. ITEMS SPECIFICATIONS ITEMS SPECIFICATIONS DOOR DESIGN Side Rounded VEGETABLE TRAY Opaque Drawer Type H) 20cu.ft COMPRESSOR PTC Starting Type DIMENSIONS (inches) H) 22cu.ft Dispenser EVAPORATOR Fin Tube Type H) 22cu.ft CONDENSER Wire Condenser 238.4 (20cu.ft) REFRIGERANT...

  • Page 4: Parts Identification

    2. PARTS IDENTIFICATION Filter (inside) Digital Sensor Control Dairy Bin Refrigerator Light Shelves Design-A-Door Egg Box Chef Fresh/ Snack Pan Optibin Crisper Can Dispenser Keeps fruits and vegetable fresh and crisp Refrigerator Custom cube Icemaker Door Rack Ice Bin Freezer Light Durabase Basket Wire Divider...

  • Page 5: Disassembly

    3. DISASSEMBLY 3-1 DOOR Freezer Door 1. Loosen the hexagonal bolts attaching the lower hinge to Refrigerator Door the body to remove the refrigerator door only. 1. Remove the hinge cover by pulling it upwards. 2. Loosen the hexagonal bolts attaching the upper hinge to the body and lift the freezer door.

  • Page 6: Fan And Fan Motor

    3-3 FAN AND FAN MOTOR 3-5-1 Refrigerator Compartment Lamp 1. Unplug the power cord from the outlet. 1. Remove the freezer shelf. (If your refrigerator has an icemaker, remove the icemaker first) 2. Remove refrigerator shelves. 2. Remove the grille by pulling it out and by loosening a 3.

  • Page 7: Adjustment

    4. ADJUSTMENT 4-1 COMPRESSOR 4-2-3 PTC-Applied Circuit Diagram Starting Method for the Motor 4-1-1 Role The compressor intakes low temperature and low pressure gas from the evaporator of the refrigerator and compresses OVERLOAD PROTECTOR this gas to high-temperature and high-pressure gas. It then delivers the gas to the condenser.

  • Page 8: Olp (Overload Protector)

    4-3 OLP (OVERLOAD PROTECTOR) 4-4 TO REMOVE THE COVER PTC 4-3-1 Definition of OLP (1) OLP (OVERLOAD PROTECTOR) is attached to the Compressor and protects the Motor by opening the circuit to the Motor if the temperature rises and activating the bimetal spring in the OLP. (2) When high current flows to the Compressor motor, the Bimetal works by heating the heater inside the OLP, and the OLP protects the Motor by cutting off the...

  • Page 9: Circuit Diagram

    5. CIRCUIT DIAGRAM 3854JK1006A GY: GRIS/GRAY 3854JK1006B GY: GRIS/GRAY - 9 -...

  • Page 10: Troubleshooting

    6. TROUBLESHOOTING 6-1 COMPRESSOR AND ELECTRIC COMPONENTS (Reated Voltage Remove PTC-Starter Power Source. ±10%)? from Compressor and measure voltage between Terminal C of Compressor and Terminals 5 or 6 of PTC. OLP disconnected? No Voltage. Replace OLP. Check connection condition. Reconnect.

  • Page 11: Ptc And Olp

    6-2 PTC AND OLP Normal operation of Separate PTC-Starter Observation value is Compressor is from Compressor and 115V/60Hz : 6.8Ω±30% measure resistance impossible or poor. between No. 5 and 6 of PTC-Starter with a Tester. (Figure 14) Replace PTC- The resistance value Starter.

  • Page 12: Other Electrical Components

    6-3 OTHER ELECTRICAL COMPONENTS M Not cooling at all Check for open short or Compressor Cause incorrect resistance readings doesn't run. in the following components a. Starting devices Short, open, or broken. Poor contact b. OLP or shorted. Coil open or shorted. c.

  • Page 13: Service Diagnosis Chart

    6-4 SERVICE DIAGNOSIS CHART COMPLAINT POINTS TO BE CHECKED REMEDY No Cooling. • Is the power cord unplugged from the outlet? • Plug into the outlet. • Check if the power switch is set to OFF. • Set the switch to ON. •...

  • Page 14: Refrigeration Cycle

    6-5 REFRIGERATION CYCLE M Troubleshooting Chart TEMPERATURE STATE OF STATE OF THE CAUSE REMARKS OF THE THE UNIT EVAPORATOR COMPRESSOR PARTIAL Freezer Low flowing sound of A little higher • Refrigerant level is low due LEAKAGE compartment and Refrigerant is heard and than ambient •...
  • Page 15 M General Control of Refrigerating Cycle ITEMS UNIT STANDARDS PURPOSES REMARKS Pipe and Min. Pipe: within 1 hour. To protect The opening time should be reduced piping system Comp: within 10 minutes. moisture to a half of the standards during rain opening time Drier: within 20 minutes.

  • Page 16: Operation Principle & Repair Method Of Icemaker

    7. OPERATION PRINCIPLE AND REPAIR METHOD OF ICEMAKER 7-1 OPERATION PRINCIPLE 7-1-1 Operation Principle of IceMaker Power On Start Position • Adjusts EJECTOR to Start Position with power on. Ice Making • Waits until water becomes cold after starting the Mode ice making operation.
  • Page 17 7-2 CONTROL METHOD ACCORDING TO FUNCTIONS 7-2-1 Start Position 1. After POWER OFF or Power Outage, check the EJECTOR's position with MICOM initialization to restart. 2. How to check if it is in place: - Check HIGH/LOW signals from HALL SENSOR in MICOM PIN. 3.
  • Page 18 7-2-4 Fill / Park Position 1. When Ice-Removing control (Normal Ice-Removing control, Ice-Removing control for test) has completed, and the EJECTOR is in place, this control operates the ICE SOLENOID by time check in the compressor enclosure of the refrigerator. Then it supplies water to the ice making tray. 2.
  • Page 19 7-2-5 Function TEST 1. This is a compulsory operation for TEST, SVC, cleaning, etc. It is operated by pressing the water supply control KEY for 3 seconds. 2. It operates in the Ice Making mode, but not in the Ice-Removing mode or water supply process. (If there is an ERROR, it can only be checked in the TEST mode.) 3.

  • Page 20: Description Of Function & Circuit Of Micom

    8. DESCRIPTION OF FUNCTION & CIRCUIT OF MICOM 8-1 FUNCTION 8-1-1 Function 1. When the appliance is plugged in, it is set to 37 °F for the Refrigerator and 0 °F for the Freezer. You can adjust the Refrigerator and the Freezer control temperature by pressing the COLDER button or the WARMER button.
  • Page 21 8-1-4 CONTROL OF FREEZER FAN MOTOR 1. Freezer fan motor has high and standard speeds. 2. High speed is used at power-up, for express freezing, and when refrigerator is overloaded. Standard speeds is used for general purposes. 3. To improve cooling speed, the RPM of the freezer fan motor change from normal speed to high. 4.
  • Page 22 8-1-8 Buzzer Sound When the button on the front Display is pushed, a Ding~ Dong~ sound is produced. (Refer to the Buzzer Circuit 8-2-4 No. 3) 8-1-9 Defrosting (removing frost) 1. Defrosting starts each time the COMPRESSOR running time reaches 7 hours. 2.
  • Page 23 8-1-13 Defect Diagnosis Function 1. Automatic diagnosis makes servicing the refrigerator easy. 2. When a defect occurs, the buttons will not operate; but the tones. such as ding. will sound. 3. When the defect CODE removes the sign, it returns to normal operation (RESET). 4.
  • Page 24 8-1-14 TEST Mode 1. The Test mode allows checking the PCB and the function of the product as well as finding out the defective part in case of an error. 2. The test mode is operated by pressing two buttons at Display panel. 3.
  • Page 25 8-2 PCB FUNCTION 8-2-1 Power Circuit The secondary part of the TRANSFORMER is composed of the power supply for the display, the BLDC FAN Motor drive (15.5 V), the relay drive (12 Vdc) and the MICOM and IC (5 Vdc). The voltage for each part is as follows: PART VA 1...
  • Page 26 8-2-2 Oscillation Circuit This circuit generates the base clock for calculating time and the synchro clock for transmitting data from and to the inside logic elements of the IC1 (MICOM). Be sure to use specific replacement parts, since calculating time by the IC1 may be changed.
  • Page 27 8-2-4 Load / Buzzer Drive & Open Door Detection Circuit 1. Load Drive Condition Check FREEZER DOOR SWITCH REFRIGERATOR DOOR SWITCH VALVE DEFROSTING COMP LAMP LOAD TYPE POWER MODE (DISPENSER HEATER (OPTIONAL) MDL) Measurement Location (IC6) NO.13 NO.14 NO.16 NO.12 NO.15 1V or below Condition...
  • Page 28 3. Buzzer Drive Condition Check Condition Tone (Ding~Dong~) when the button on Alarm for open door Measure- the display is pushed. (beep-beep-beep) ment Location 0.05 s 0.2 s 0.1 s 0.5 s 0.5 s IC1 ( 2.63 kz (Ding~) 2.21 kz (Dong~) IC1 ( 2.63 kz (Beep~) 4.
  • Page 29 8-2-5 Temperature Sensor Circuit FREEZER-SENSOR REFRIGERATOR-SENSOR DEFROST-SENSOR The upper CIRCUIT reads REFRIGERATOR temperature, FREEZER Temperature, and DEFROST-SENSOR temperature for defrosting and the indoor temperature for compensating for the surrounding temperature into MICOM. OPENING or SHORT state of each TEMPERATURE SENSOR are as follows: SENSOR CHECK POINT NORMAL (-30°C ~ 50°C)
  • Page 30 8-2-6 Refrigeration Compartment Stepping Motor Damper Circuit * The circuit shown below is the damper circuit to regulate the refrigerator temperature. 8-2-7 Dispenser Input/LED Output Circuit PUMP SWITCH - 30 -...
  • Page 31 8-2-8 Temperature Compensation & Overcooling/Undercooling Compensation Circuit 1. Refrigerator Temperature Compensation ➧ Table of Temperature Compensation by adjusting the Refrigerator resistance (difference from the current temperature) Resistance Temperature Remark e.g., If the refrigerator compensation resistance (RCR) Compensation (RCR) is changed from 10K (the current resistance) to 18K (the adjustment resistance), the temperature 180 KΩ...
  • Page 32 8-2-9 Key Button Input & Display Light-On Circuit ➧ The circuit shown above determines whether a function control key on the operation display is pushed. It also turns on the corresponding function indication LED (LED Module) SEVEN SEGMENT DISPLAY (SEVEN SEGMENT DISPLAY MODULE).
  • Page 33 8-3 RESISTANCE SPECIFICATION OF SENSOR TEMPERATURE DETECTED RESISTANCE OF FREEZER RESISTANCE OF REFRIGERATOR & BY SENSOR SENSOR DEFROST SENSOR & ROOM SENSOR - 20 ˚C 22.3 KΩ 77 KΩ - 15 ˚C 16.9 KΩ 60 KΩ - 10 ˚C 13.0 KΩ 47.3 KΩ...
  • Page 34 - 34 -...
  • Page 35 - 35 -...
  • Page 36 8-5 MAIN PWB ASSEMBLY AND PARTS LIST 8-5-1 Main PWB Assembly - 36 -...
  • Page 37 8-5-2 Replacement Parts List - 37 -...
  • Page 38 8-5-3 PWB Assembly, Display, And Parts List Dispenser Model Best Model SW106 - 38 -...
  • Page 39 8-6 PWB DIAGRAM 8-6-1 PWB Main Assembly FREEZER DOOR SWITCH REFRIGERATOR DOOR SWITCH PWB ASSEMBLY - 39 -...
  • Page 40 REFRIGERATOR DOOR SWITCH FREEZER SENSOR REFRIGERATOR SENSOR DEFROST SENSOR FREEZER DOOR SWITCH - 40 -...

  • Page 41: Exploded View & Replacement Parts List

    9. EXPLODED VIEW & REPLACEMENT PARTS LIST CASE PARTS CASE PARTS CAUTION: Use the part number to order part, not the position number. CAUTION: Use the part number to order part, not the position number. 103B 281A 284D 281B 611D 103A 410A 611B...
  • Page 42 FREEZER PARTS(Drawer) CAUTION: Use the part number to order part, not the position number. 285A 125A 145C 248B 136B 145G 248A 145F 145K 145E 248F 248E 145J 131A 237C 145D 249G 136A : on some models - 42 -...
  • Page 43 REFRIGERATOR PARTS CAUTION: Use the part number to order part, not the position number. 147C 147B 141D 147A 149C 141A 149E 140B 141E 143E 140B 141C 140D 140F 140E 142A 142D 143F 142D 140B 140B 142E 142E 128A 128A 170A 146A 128M 168A...
  • Page 44 DOOR PARTS(Drawer) CAUTION: Use the part number to order part, not the position number. 230A 241A 233A 231A 241B 244J 241C 244E 241E 237A 244H 237A 700C 241D 700A 243A 244M 205D 205C 249A 128D 200A 248C 621A 203A 201A 205A 212B 700B...
  • Page 45 DOOR PARTS CAUTION: Use the part number to order part, not the position number. 230A 147D 241A 233A 231A 241B 244B 607A 501B 616B 279B 241C 241E 621B 120H 237A 244A 276B 113C 279C 406C 616A 237A 281F 241D 243A 249A 607A 128D...
  • Page 46 ICE MAKER PARTS CAUTION: Use the part number to order part, not the position number. 602A 600A 615A : on some models - 46 -...
  • Page 47 ICE & WATER PARTS CAUTION: Use the part number to order part, not the position number. 623C 623B 625A 616D 627A 623A 623C 616G 622A 616F 618A 616D 627A 627A 619B - 47 -...
  • Page 48 D E S C R I P T I O N L R D C 2 0 7 3 1 S T L R D C 2 0 7 3 1 W W L R D C 2 0 7 3 1 S W L R D C 2 0 7 3 1 T T L R D N 2 0 7 2 0 B K 1 0 3 A...
  • Page 49 D E S C R I P T I O N L R D C 2 0 7 3 1 S T L R D C 2 0 7 3 1 W W L R D C 2 0 7 3 1 S W L R D C 2 0 7 3 1 T T L R D N 2 0 7 2 0 B K 2 0 1 A...
  • Page 50 L O C D E S C R I P T I O N L R D C 2 0 7 3 1 S T L R D C 2 0 7 3 1 W W L R D C 2 0 7 3 1 S W L R D C 2 0 7 3 1 T T L R D N 2 0 7 2 0 B K 3 1 0 A...
  • Page 51 DESCRIPTION LRDN20720BQ LRDN20720ST LRDN20720WW LRDN20725SW LRDN20725TT 103A HANDLE,B ACK 3650JJ2003B 3650JJ2003L 3650JJ2003A 3650JJ2003A 3650JJ2003L 103B HANDLE,B ACK 3650JJ2003F 3650JJ2003M 3650JJ2003E 3650JJ2003E 3650JJ2003M 103C COVER ASSEMBLY,LOWER 3551JJ1015C 3551JJ1015E 3551JJ1015A 3551JJ1015A 3551JJ1015E 105A DRAIN ASSEMBLY,PIPE-Z 5251JJ2003A 5251JJ2003A 5251JJ2003A 5251JJ2003A 5251JJ2003A 105F SKIRT,LOWER 5070JJ3002A 5070JJ3002A 5070JJ3002A...
  • Page 52 DESCRIPTION LRDN20720BQ LRDN20720ST LRDN20720WW LRDN20725SW LRDN20725TT 212A HANDLE,F 3650JJ1017D 3650JJ1017J 3650JJ1017D 212B HANDLE,F 3650JJ0005B 3650JJ0005A 212G NAME PLATE,P( H) 4140JD2001C 4140JD2001C 4140JD2001C 4140JD2001C 4140JD2001C 230A DOOR ASSEMBLY,R 3581JJ8027S 3581JJ8027C 3581JJ8027N 3581JJ8027B 3581JJ8027D 231A DOOR FOAM ASSEMBLY,R 5433JJ0016F 5433JJ0016E 5433JJ0016C 5433JJ0016B 5433JJ0016L 233A GASKET ASSEMBLY,DOOR...
  • Page 53 DESCRIPTION LRDN20720BQ LRDN20720ST LRDN20720WW LRDN20725SW LRDN20725TT 307A COMPRESSOR,SET ASSEMBLY 2521JJ8007A 2521JJ8007A 2521JJ8007A 2521JJ8007A 2521JJ8007A 308A P.T.C ASSEMBLY 6749C-0008D 6749C-0008D 6749C-0008D 6749C-0008D 6749C-0008D 309A O.L.P 6750C-0004S 6750C-0004S 6750C-0004S 6750C-0004S 6750C-0004S 310A COVER,P.T.C 3550JA2042A 3550JA2042A 3550JA2042A 3550JA2042A 3550JA2042A 312A RUBBER,SEAT 5040JA3031A 5040JA3031A 5040JA3031A 5040JA3031A 5040JA3031A...
  • Page 54 DESCRIPTION LRDN22725TT LRDN22725SW LRDN22720ST LRDN22720BQ LRDN22720BK 103A HANDLE,B ACK 3650JJ2003L 3650JJ2003A 3650JJ2003L 3650JJ2003B 3650JJ2003L 103B HANDLE,B ACK 3650JJ2003M 3650JJ2003E 3650JJ2003M 3650JJ2003F 3650JJ2003M 103C COVER ASSEMBLY,LOWER 3551JJ1015F 3551JJ1015B 3551JJ1015F 3551JJ1015D 3551JJ1015F 105A DRAIN ASSEMBLY,PIPE-Z 5251JJ2003A 5251JJ2003A 5251JJ2003A 5251JJ2003A 5251JJ2003A 105F SKIRT,LOWER 5070JJ3002A 5070JJ3002A 5070JJ3002A...
  • Page 55 DESCRIPTION LRDN22725TT LRDN22725SW LRDN22720ST LRDN22720BQ LRDN22720BK 212B HANDLE,F 3650JJ0005B 3650JJ0005C 212G NAME PLATE,P( H) 4140JD2001C 4140JD2001C 4140JD2001C 4140JD2001C 4140JD2001C 230A DOOR ASSEMBLY,R 3581JJ8024D 3581JJ8024B 3581JJ8024C 3581JJ8024S 3581JJ8024T 231A DOOR FOAM ASSEMBLY,R 5433JJ0019L 5433JJ0019B 5433JJ0019E 5433JJ0019F 5433JJ0019H 233A GASKET ASSEMBLY,DOOR 4987JJ1004F 4987JJ1004B 4987JJ1004F 4987JJ1004B...
  • Page 56 DESCRIPTION LRDN22725TT LRDN22725SW LRDN22720ST LRDN22720BQ LRDN22720BK 307A COMPRESSOR,SET ASSEMBLY 2521JJ8007A 2521JJ8007A 2521JJ8007A 2521JJ8007A 2521JJ8007A 308A P.T.C ASSEMBLY 6749C-0008D 6749C-0008D 6749C-0008D 6749C-0008D 6749C-0008D 309A O.L.P 6750C-0004S 6750C-0004S 6750C-0004S 6750C-0004S 6750C-0004S 310A COVER,P.T.C 3550JA2042A 3550JA2042A 3550JA2042A 3550JA2042A 3550JA2042A 312A RUBBER,SEAT 5040JA3031A 5040JA3031A 5040JA3031A 5040JA3031A 5040JA3031A...
  • Page 57 L O C D E S C R I P T I O N L R D N 2 2 7 2 0 W W L R D N 2 2 7 1 1 T T L R D N 2 2 7 1 1 S W L R D C 2 2 7 3 1 W W L R D C 2 2 7 3 1 T T 1 0 3 A...
  • Page 58 D E S C R I P T I O N L R D N 2 2 7 2 0 W W L R D N 2 2 7 1 1 T T L R D N 2 2 7 1 1 S W L R D C 2 2 7 3 1 W W L R D C 2 2 7 3 1 T T 2 0 3 A...
  • Page 59 L O C D E S C R I P T I O N L R D N 2 2 7 2 0 W W L R D N 2 2 7 1 1 T T L R D N 2 2 7 1 1 S W L R D C 2 2 7 3 1 W W L R D C 2 2 7 3 1 T T 3 1 4 A...
  • Page 60 DESCRIPTION LRDC22731SW LRDC22731ST LRDC22743TT LRDC22743SW LRDC22743ST 103A HANDLE,B ACK 3650JJ2003A 3650JJ2003L 3650JJ2003L 3650JJ2003A 3650JJ2003L 103B HANDLE,B ACK 3650JJ2003E 3650JJ2003M 3650JJ2003M 3650JJ2003E 3650JJ2003M 103C COVER ASSEMBLY,LOWER 3551JJ1015B 3551JJ1015F 3551JJ1015F 3551JJ1015B 3551JJ1015F 105A DRAIN ASSEMBLY,PIPE-Z 5251JJ2003A 5251JJ2003A 5251JJ2003A 5251JJ2003A 5251JJ2003A 105F SKIRT,LOWER 5070JJ3002A 5070JJ3002A 5070JJ3002A...
  • Page 61 DESCRIPTION LRDC22731SW LRDC22731ST LRDC22743TT LRDC22743SW LRDC22743ST 158A COVER,LAMP 3550JJ1040A 3550JJ1040A 3550JJ1040A 3550JJ1040A 3550JJ1040A 158E COVER,LAMP 3550JJ1051A 3550JJ1051A 3550JJ1051A 3550JJ1051A 3550JJ1051A 160A GLASS,SHELF 4890JL1002K 4890JL1002K 4890JL1002K 4890JL1002K 4890JL1002K 160B DECO,TRAY 3806JL2005D 3806JL2005D 3806JL2005D 3806JL2005D 3806JL2005D 161A COVER,TRAY 3550JJ2026A 3550JJ2026A 3550JJ2026A 3550JJ2026A 3550JJ2026A 168A COVER,MAGIC ROOM...
  • Page 62 DESCRIPTION LRDC22731SW LRDC22731ST LRDC22743TT LRDC22743SW LRDC22743ST 503C PWB(PCB) ASSEMBLY,DISPLAY 6871JB2046B 6871JB2046B 6871JB2046A 6871JB2046A 6871JB2046A 503D CASE,DISPLAY 3110JJ1005A 3110JJ1005A 3110JJ1005A 3110JJ1005A 3110JJ1005A 503E COVER,DISPLAY 3550JJ2032A 3550JJ2032A 3550JJ2032A 3550JJ2032A 3550JJ2032A 600A ICE MAKER ASSEMBLY,KIT 5989JA0002A 5989JA0002A 5989JA0002A 5989JA0002A 5989JA0002A 602A HOLDER,BRACKET 4930JA3037A 4930JA3037A 4930JA3037A 4930JA3037A...
  • Page 63 November, 2004 Printed in Mexico P/No. 3828JL8005A...

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