LG LFC21760ST Service Manual
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LG LFC21760ST Service Manual

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REFRIGERATOR
SERVICE MANUAL
CAUTION
BEFORE SERVICING THE PRODUCT,
READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
MODELS:
LFC21760ST
LFC25760SB
LFC25760ST
LFC25760SW
COLORS: WESTERN BLACK(SB)
LFC25760TT
TITANIUM(TT)
SUPER WHITE(SW)
STAINLESS(ST)

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Summary of Contents for LG LFC21760ST

  • Page 1 REFRIGERATOR SERVICE MANUAL CAUTION BEFORE SERVICING THE PRODUCT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL. MODELS: LFC21760ST LFC25760SW COLORS: WESTERN BLACK(SB) LFC25760SB LFC25760TT TITANIUM(TT) LFC25760ST SUPER WHITE(SW) STAINLESS(ST)

  • Page 2: Table Of Contents

    CONTENTS SAFETY PRECAUTIONS ............................... 2 SPECIFICATIONS................................... 3 PARTS IDENTIFICATION ............................... 4 DISASSEMBLY.................................. 5-10 DOOR....................................5-6 DOOR ALIGNMENT................................6 HOW TO REMOVE AND REINSTALL THE PULLOUT DRAWER..................7-9 ADJUSTMENT ................................. 10-11 COMPRESSOR.................................. 10 PTC-STARTER................................... 10 OLP (OVERLOAD PROTECTOR)............................11 TO REMOVE THE COVER PTC ............................11 CIRCUIT DIAGRAM................................

  • Page 3: Specifications

    1. SPECIFICATIONS ITEMS SPECIFICATIONS ITEMS SPECIFICATIONS DOOR DESIGN Side Rounded VEGETABLE TRAY Opaque Drawer Type COOLING SYSTEM Fan Cooling COMPRESSOR PTC Starting Type TEMPERATURE CONTROL Micom Control EVAPORATOR Fin Tube Type Full Automatic CONDENSER Wire Condenser DEFROSTING SYSTEM Heater Defrost REFRIGERANT R-134a (115 g) DOOR FINISH...

  • Page 4: Parts Identification

    2. PARTS IDENTIFICATION Digital Sensor Control Dairy Bin Refrigerator Light Egg Box Shelves Modular Door Bin Modular Door Bin Bottle Holder Optibin Crisper Keeps fruits and vegetable fresh Modular Door Bin and crisp Glide'N'Serve Customcube Icemaker Pullout Drawer Ice Bin Durabase Tilt- Out Door Basket...

  • Page 5: Disassembly

    3. DISASSEMBLY 3-1 DOOR Refrigerator door 1. Remove the top hinge cover and disconnect the wire Gasket harness. Door Bracket Clip 2. Remove the ground screw. Frame 3. Rotate the lever hinge and lift off hinge. 4. Lift off the refrigerator door. Flat Tip Screwdriver 5.

  • Page 6: Door Alignment

    2. Insert gasket into channel 3-2 DOOR ALIGNMENT 1) Snap gasket assembly into the door bracket. If the space between your doors is uneven, follow the Inserting the gasket assembly into the bracket door instructions below to align the doors: 1.

  • Page 7: How To Remove And Reinstall The Pullout Drawer

    3-3 HOW TO REMOVE AND REINSTALL THE PULLOUT DRAWER 3-3-1 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 Step 4) Lift the freezer door up to unhook it from the rail from each side).
  • Page 8 3-3-2 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 Step 3) Insert the rail into the left side gear, and insert the need to be perpendicular to each other.
  • Page 9 3-3-3 PULL OUT DRAWER To separate the drawer, push the front left and right hooks in direction to pull up and remove. Then gently lift the gear part of rear left and right side of the drawer and pull it out in direction.

  • Page 10: 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 11: 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 current...

  • Page 12: Circuit Diagram

    5. CIRCUIT DIAGRAM BETTER MODEL - 12 -...

  • Page 13: Troubleshooting

    6. TROUBLESHOOTING 6-1 COMPRESSOR AND ELECTRIC COMPONENTS (Rated voltage Remove PTC-Starter Power source. ±10%)? from compressor and measure voltage between terminal C of compressor and terminal 5 or 6 of PTC. OLP disconnected? No voltage. Replace OLP. Check connection condition. Reconnect.

  • Page 14: 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 19) Replace PTC- The resistance value Starter.

  • Page 15: 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 16: 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 17: 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 18 6-5-1 SEALED SYSTEM DIAGNOSIS Not Cooling Complaint All components operating, No airflow problems, Not frosted up as a defrost problem problem has been isolated to sealed system area Frost None Partial Pattern? Equalization Equalization Test Test Very Fast Very Slow Very Slow Fast Very Fast...

  • Page 19: Operation Principle And 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 ¥ Adjusts EJECTOR to with power on. Start Position Start Position Icemaking ¥ Waits until water becomes cold after starting the Mode icemaking operation.
  • Page 20 7-2 ICE MAKER 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 21 7-2-4 Fill/Park Position 1. Once a normal harvest mode has been completed, the water solenoid will be activated. 2. The amount of water is adjusted by pressing the fill key repeatedly. This changes the time allowed for fill as illustrated in the table below.
  • Page 22 7-2-5 Function TEST 1. This is a compulsory operation for test, service, cleaning, etc. It is operated by pressing and holding the fill key for 3 seconds. 2. The test works only in the icemaking mode. It cannot be entered from the harvest or fill mode. (If there is an ERROR, it can only be checked in the test mode.) 3.

  • Page 23: Description Of Function And 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 defaults 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 ADJUST button. 2.
  • Page 24 8-1-6 Alarm for Open Door 1. This feature sounds a buzzer when the freezer or refrigerator door is not closed within 1 minute after it is opened. 2. One minute after the door is opened, the buzzer sounds three times each for 1/2 second. These tones repeat every 30 seconds.
  • Page 25 8-1-9 Electrical Parts Are Turned On Sequentially Electrical parts such as compressor, defrosting heater, freezer fan, etc. are turned on in the following order to prevent noise and parts damage. Several parts are started at the same time at initial power on and are turned off together when test is completed.
  • Page 26 8-1-10 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 27 8-1-11 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 on the display panel. 3.
  • Page 28 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 29 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 specified replacement parts, since calculating time by the IC1 may be changed.
  • Page 30 8-2-4 Load / Buzzer Drive & Open Door Detection Circuit 1. Load Drive Condition Check FRENCH DEFROSTING WATER LAMP-F COMP LOAD TYPE LAMP-R DOOR VALVE/VALVE2 HEATER HEATER Measurement Location (IC6) NO.16 NO.11 NO.12 NO.13 NO.14 NO.15 1V or below Condition 2.
  • Page 31 2. Open Door Detection Circuit Check Measurement Location Freezer/ (PIN NO.30 & PIN NO.27) Refrigerator Door Closed Open - 31 -...
  • Page 32 8-2-5 Temperature Sensor Circuit 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 33 8-3 RESISTANCE SPECIFICATION OF SENSOR RESISTANCE OF FREEZER RESISTANCE OF REFRIGERATOR & TEMPERATURE 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 - 5 ˚C 10.1 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 - 38 -...
  • Page 39 8-6 PWB DIAGRAM 8-6-1 PWB Main Assembly - 39 -...
  • Page 40 - 40 -...

  • Page 41: Exploded View And Replacement Parts List

    9. EXPLODED VIEW & REPLACEMENT PARTS LIST CASE PARTS CAUTION: Use the part number to order part, not the position number. 207B 402A 103B 271C 271B 103A 410A 207A 409D 406D 501F 503C 402A 271B 271A 282F 503D 410G 145A 503G 500A 503E...
  • Page 42 FREEZER PARTS CAUTION: Use the part number to order part, not the position number. 250C 250D 145C 250E 250D 145G 250C 136B 145J 131A 145L 145F 145M 145K 145H 237C 136A - 42 -...
  • Page 43 REFRIGERATOR PARTS CAUTION: Use the part number to order part, not the position number. 147C 141B 141A 147B 147A 141B 141C 141A 141B 141A 141C 141B 141A 141C 146A 161F 141D 141C 161A 167B 154A 161D 160B 151A 161C 248A 155J 161E 146B...
  • Page 44 DOOR PARTS CAUTION: Use the part number to order part, not the position number. 230B 230A 231B 233B 233C 233D 233A 231A 241A 234C 241B 234B 234D 234A 212G 241C 237A 241C 237A 244E 241C 244E 241C 241C 243C 243C 243A 243A 243B...
  • Page 45 WATER AND ICEMAKER PARTS CAUTION: Use the part number to order part, not the position number. 602A 600A 616E 616K 623A 623B 627B 619A - 45 -...
  • Page 46 P/No. 3828JD8990C MAR., 2006 Printed in Korea...

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Lfc25760swLfc25760sbLfc25760ttLfc25760st

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