LG LRFC25750ST Service Manual Download Page 31

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8-3 RESISTANCE SPECIFICATION OF SENSOR

• The resistance of the SENSOR has a ±5% common difference.
• Measure the resistance of the SENSOR after leaving it for over 3 minutes in the measuring temperature.

This delay is necessary due to sensor response speed.

• Measure the F-SENSOR, SUPER FROST SENSOR, R1, R2-SENSOR after disconnect CON5 of PWB ASSY, MAIN.

TEMPERATURE

RESISTANCE OF FREEZER

RESISTANCE OF REFRIGERATOR &

SENSOR

DEFROST SENSOR & ROOM SENSOR

- 20 ˚C (-4 °F)

22.3 K

Ω

77 K

Ω

- 15 ˚C (5 °F)

16.9 K

Ω

60 K

Ω

- 10 ˚C (14 °F)

13.0 K

Ω

47.3 K

Ω

- 5 ˚C (23 °F)

10.1 K

Ω

38.4 K

Ω

0 ˚C (32 °F)

7.8 K

Ω

30 K

Ω

+ 5 ˚C (41 °F)

6.2 K

Ω

24.1 K

Ω

+ 10 ˚C (50 °F)

4.9 K

Ω

19.5 K

Ω

+ 15 ˚C (59 °F)

3.9 K

Ω

15.9 K

Ω

+ 20 ˚C (68 °F)

3.1 K

Ω

13 K

Ω

+ 25 ˚C (77 °F)

2.5 K

Ω

11 K

Ω

+ 30 ˚C (86 °F)

2.0 K

Ω

8.9 K

Ω

+ 40 ˚C (104 °F)

1.4 K

Ω

6.2 K

Ω

+ 50 ˚C (122 °F)

0.8 K

Ω

4.3 K

Ω

Summary of Contents for LRFC25750ST

Page 1: ...CING THE UNIT READ THE SAFETY PRECAUTIONS IN THIS MANUAL REFRIGERATOR SERVICE MANUAL LRFC25750 COLOR COLOR WESTERN BLACK TITANIUM http biz lgservice com MODEL LRFC25750ST LRFC21755SB LRFC21755ST STAINLESS STEEL LRFC21755TT ...

Page 2: ...g your refrigerator 1 Check the refrigerator for current leakage 2 To prevent electric shock unplug before servicing 3 Always check line voltage and amperage 4 Use standard electrical components 5 Don t touch metal products in the freezer with wet hands This may cause frostbite 6 Prevent water from spiling onto electric elements or the machine parts 7 Close the top door before opening the bottom d...

Page 3: ...RATURE CONTROL Micom Control Full Automatic DEFROSTING SYSTEM Heater Defrost DOOR FINISH Embossed Metal VCM Stainless HANDLE TYPE Bar INNER CASE ABS Resin INSULATION Polyurethane Foam ITEMS SPECIFICATIONS VEGETABLE TRAY Opaque Drawer Type COMPRESSOR PTC Starting Type EVAPORATOR Fin Tube Type CONDENSER Wire Condenser REFRIGERANT R 134a 115 g LUBRICATING OIL Freol 10G 310 cc DEFROSTING DEVICE SHEATH...

Page 4: ...igerator Light Shelves Optibin Crisper Keeps fruits and vegetable fresh and crisp Customcube Icemaker Glide N Serve Ice Bin Durabase Divider Pull out Drawer Freezer Door Rack Tilting Design A Door Design A Door Wine Holder Dairy Bin Egg Box Design A Door ...

Page 5: ...t the freezer door 3 Pull out the door gasket to remove from the door foam assembly Freezer Door 1 Loosen the hex head bolts attaching the lower hinge to the body to remove the refrigerator door only 2 Pull out the door gasket to remove from the door foam assembly 3 DISASSEMBLY 5 HINGE HINGE COVER Figure 1 GASKET Figure 2 LOWER HINGE BOLT Figure 3 ...

Page 6: ...cord from the outlet 2 Remove refrigerator shelves 3 Release the hooks on both ends of the lamp shield and pull the shield downward to remove it 4 Turn the lamp counterclockwise 5 Assemble in reverse order of disassembly Replacement bulb must be the same specification as the original Max 60 W2EA 3 4 2 Freezer Compartment Lamp 1 Unplug refrigerator or disconnect power 2 Reach behind light shield to...

Page 7: ...t flow to both the start winding and main winding 4 2 3 PTC Applied Circuit Diagram Starting Method for the Motor 4 2 4 Motor Restarting and PTC Cooling 1 It requires approximately 5 minutes for the pressure to equalize before the compressor can restart 2 The PTC device generates heat during operation Therefore it must be allowed to cool before the compressor can restart 4 2 5 Relation of PTC Star...

Page 8: ... Cover Back M C 2 Remove the screw on Cover PTC 3 Remove two Housings on upper part of Cover PTC 4 Take out the cover PTC from upper to lower position like 5 Turn 45 in the direction of and take it out 6 Assembly in reverse order of disassembly 8 Part Customer part number Lot code date code 330 FBYY S1 BOX98 12345678 Physical termination part number Electrical characteristics part number No Name B...

Page 9: ...BETTER MODEL 5 CIRCUIT DIAGRAM 9 ...

Page 10: ...y needs to be checked by an electrician Replace Compressor Supply voltage rating with 10 Applied voltage isn t in range of Rating Voltage 10 Remove PTC Starter from Compressor and measure voltage between Terminal C of Compressor and Terminals 5 or 6 of PTC Check resistance between M C S C and M S in Motor Compressor Check resistance of two terminals in PTC Starter Check resistance of two terminals...

Page 11: ...ure resistance between No 5 and 6 of PTC Starter with a Tester Figure 14 Separate OLP from Compressor and check resistance value between two terminals of OLP with a Tester Figure 15 Observation value is 115V 60Hz 6 8Ω 30 The resistance value is 0Ω short or open Check another electric component Replace OLP Replace PTC Starter Figure 14 Figure 15 ...

Page 12: ...apacity Replace indicated component Advise customer that the Power supply needs to be checked by an electrician Replace indicated component Cause Check voltage at starting devices Check current flowing in sub coil of Compressor Check rating of OLP Fan motor doesn t run Heavy frost buildup on EVAPORATOR Wire is open or shorted Coil is shorted or open Open Open Replace Defrost Heater Replace indicat...

Page 13: ...high Is there a gap in the door gasket Is the unit positioned in a firm and even place Are any unnecessary objects placed in the back side of the unit Check if the Drip Tray is not firmly fixed Check if the cover of the compressor enclosure in the lower front side is taken out Check if the door gasket is dirty with an item like juice Is the refrigerator level Is there too much food in the refriger...

Page 14: ...or don t in inlet only temperature The capillary tube is faulty cool normally WHOLE Freezer Flowing sound of refrigerant Equal to ambient Normal discharging of the CLOG compartment and is not heard and frost isn t temperature Refrigerant Refrigerator don t cool formed MOISTURE Cooling operation Flowing sound of refrigerant Lower than Cooling operation restarts CLOG stops periodically is not heard ...

Page 15: ...ial Very Fast Inefficient Compressor Partial Restriction Complete Restriction Equalization Test Condenser Temperature None Very Fast Very Slow Very Slow Hotter than Normal Air Low Side Leak Loss of Change Compressor Not Pumping Cap Tube Sound Room Temperature Trace of Oil Undercharge Leak Yes No Faint Fast None to Weak The equalization test is trying to restart a compressor using a start kit after...

Page 16: ...o Start Position with power on Power On Start Position Ice Making Mode Harvest Mode Park Position Fill Test Mode Waits until water becomes cold after starting the ice making operation Runs MOTOR to drop ice from the tray the ICE BIN Performs Ice Making Mode after supplying water by operating the SOLENOID in ICE VALVE To operate LINE and SERVICE press and hold the Fill Key for 3 seconds The ice mak...

Page 17: ...tive the ice making function will be completed in 4 hours NOTE After Icemaker Power is ON the Icemaker heater will be on for test for 9 sec 7 2 3 Harvest Mode 1 Ice removing control refers to the operation of dropping cubes into the ice bin from the tray when ice making has completed 2 Ice removing control mode 1 Operates Heater for 30 seconds then operate MOTOR 2 After performing Step 1 to contro...

Page 18: ...anges the time allowed for fill as illustrated in the chart Water supply amount TABLE NOTE Below is an example used by another vendor as an explanation of what is taking place 18 STAGE TIME TO SUPPLY INDICATIONS REMARKS 1 2 3 4 5 6 sec 6 5 sec 7 sec 7 5 sec 8 sec The water amount will vary depending on the water control Switch setting as well as the water pressure of the connected water line ...

Page 19: ...aker water supply control panel ERROR indicators in table can be checked only in TEST mode 19 STAGE ITEMS INDICATOR REMARKS 1 2 3 4 5 6 HEATER MOTOR HALL IC I detection of position VALVE HALL IC II detection of full filled Ice Reset Five seconds after heater starts heater will go off if temperature recorded by sensor is 10 C or lever is in up position Five seconds after heater starts you can confi...

Page 20: ... three hours the compressor and Freezer Fan will be ON The next 21hours the freezer will be controlled at the lowest temperature After 24 hours or if the Express Freezing key is pressed again the freezer will return to its previous temperature 5 For the first three hours notice the following cases 1 Compressor and freezer fan HIGH RPM continuously operate for three hours 2 If defrost starts during...

Page 21: ...zer Circuit 7 2 4 No 2 8 1 8 Defrosting removing frost 1 Defrosting starts each time the COMPRESSOR running time reaches 7 hours 2 For initial power on or for restoring power defrosting starts when the compressor running time reaches 4 hours 3 Defrosting stops if the sensor temperature reaches 46 4 F 8 C or more If the sensor doesn t reach 46 4 F 8 C in 2 hours the defrost mode is malfunctioning R...

Page 22: ...mpleted 22 OPERATING ORDERS Initial power on POWER ON in 0 5 sec in 0 5 sec Total load OFF COMP ON Freezer FAN ON in 7 min in 0 5 sec COMP ON Freezer FAN ON POWER ON COMP ON Freezer FAN ON Defrosting heater ON Defrost heater OFF in 0 5 sec in 0 5 sec in 0 5 sec in 10 sec Temperature of Defrosting Sensor is 113 F 45 C or more when unit is newly purchased or when moved Temperature of defrosting sens...

Page 23: ...e previous status 23 Defect code signs Defect code signs Better Model REFRIGERATOR TEMP COLDER WARMER 37 F IS RECOMMENDED 0 F IS RECOMMENDED FREEZER TEMP COLDER WARMER EXPRESS FREEZING NO ITEM ERROR CODE CONTENTS REMARKS 1 2 3 4 5 6 Failure of freezer sensor Failure of Refrigerator sensor Failure of defrost sensor Failure of Room Temperature sensor Failure of defrost mode Failure of BLDC Fan Motor...

Page 24: ... with 1 second interval 3 In this status all Loads are off Compressor Fan Damper Heater Even is Demonstration Mode the refrigerator Lamp automatic off function warks normally and can be demonstrated 4 It reset if you do again as clause 24 MODE MANIPULATION CONTENTS REMARKS TEST1 TEST2 TEST3 Reset Push Express Freezing Key and COLDER KEY of Freezer Temp at the Same time over 3 seconds OR Push TEST ...

Page 25: ... and the MICOM and IC 5 Vdc The voltage for each part is as follows VA1 is a part for preventing over voltage and noise When 385V or higher power is applied the inside elements are short circuited and broken resulting in blowout of the fuse in order to protect the elements of the secondary part of the TRANSFORMER 25 PART VA 1 CE 3 CE 4 CE 5 VOLTAGE 115 Vac 12 Vdc 15 5 Vdc 5 V ...

Page 26: ...ot work 8 2 3 Reset Circuit The RESET circuit allows all the functions to start at the initial conditions by initializing various parts including the RAM inside the MICOM IC1 when the power is initially supplied or the power supply to the MICOM is restored after a momentary power failure For the initial 10ms of power supply LOW voltage is applied to the MICOM RESET terminal During a normal operati...

Page 27: ...emporary change of speed for the fan motor and applies DC voltage up to 7 5V 16V to motor 3 This circuit prevents over driving the fan motor by cutting off power applied to the fan motor in the lock of fan motor by sensing the operation RPM of the fan motor 27 LOAD TYPE COMP NO 12 NO 14 NO 15 NO 13 1V or below 12V DEFROSTING HEATER LAMP FRENCH DOOR HEATER 1 2 DEW HEATER Measurement Location IC6 Co...

Page 28: ...cation Condition 0 V 5 V 0 V 5 V 0 5 s 0 5 s 2 63kz Beep OFF 0 05 s 0 1 s 0 2 s 2 s 0 V 5 V 0 V 5 V 2 63 kz Ding 2 21 kz Dong PIN NO 30 PIN NO 27 Closed 5 V Open 0 V Freezer Refrigerator Door Measurement Location A B Tone Ding Dong when the button on the display is pushed Alarm for open door beep beep beep ...

Page 29: ... OPENING or SHORT state of each TEMPERATURE SENSOR are as follows 8 2 6 Refrigeration Compartment Stepping Motor Damper Circuit The circuit shown below is the damper circuit to regulate the refrigerator temperature 29 SENSOR CHECK POINT NORMAL 30 C 50 C SHORT CIRCUITED OPEN Freezer Sensor POINT Voltage Refrigerator Sensor POINT Voltage 0 5 V 4 5 V 0 V 5 V Defrosting Sensor POINT Voltage Room Tempe...

Page 30: ... 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 The drive type is the scan type 30 ...

Page 31: ...UPER FROST SENSOR R1 R2 SENSOR after disconnect CON5 of PWB ASSY MAIN TEMPERATURE RESISTANCE OF FREEZER RESISTANCE OF REFRIGERATOR SENSOR DEFROST SENSOR ROOM SENSOR 20 C 4 F 22 3 KΩ 77 KΩ 15 C 5 F 16 9 KΩ 60 KΩ 10 C 14 F 13 0 KΩ 47 3 KΩ 5 C 23 F 10 1 KΩ 38 4 KΩ 0 C 32 F 7 8 KΩ 30 KΩ 5 C 41 F 6 2 KΩ 24 1 KΩ 10 C 50 F 4 9 KΩ 19 5 KΩ 15 C 59 F 3 9 KΩ 15 9 KΩ 20 C 68 F 3 1 KΩ 13 KΩ 25 C 77 F 2 5 KΩ 11...

Page 32: ...C is poor Replace OLP PTC after compressor shuts off COMPRESSOR RELAY is Replace MAIN PWB don t press the KEY and poor wait THE CONNECTING WIRE Check the connection of the is poor black wire of the MAIN PWB CONNECTOR CON1 2 If refrigerant is leaking Measure the amount of frost Refrigerant leakage Replace the leaking part and sticking on EVAPORATOR replace any lost refrigerant and the surface tempe...

Page 33: ...liner damaged Replace Door liner door is closed DEFROSTING is NO DEFROSTING 1 If HEATER emits heat USE TEST MODE2 HEATER disconnection Replace HEATER poor forced DEFROSTING TEMPERATURE FUSE Replace TEMPERATURE disconnection FUSE Connection is poor Check EVAPORATOR connection and wire of MAIN PWB CONNECTOR DEFROST SENSOR is poor Replace DEFROST SENSOR HEATER RELAY is poor Replace RY2 of MAIN PWB 2 ...

Page 34: ...8 5 MAIN PWB ASSEMBLY AND PARTS LIST 8 5 1 Main PWB Assembly 34 ...

Page 35: ...8 5 2 Replacement Parts List 35 ...

Page 36: ...8 5 3 PWB Assembly Display And Parts List 36 SW106 ...

Page 37: ...8 6 PWB DIAGRAM 8 6 1 PWB Main Assembly 37 ...

Page 38: ... 38 ...

Page 39: ... 411A 501F 303C 318A 303B 314A 300A 312A 317A 304A 103A 105A 301A 283B 283B 328A 418A 207B 103B 207A 271C 271B 271A 271B 315B 315B 315C 315C 323B 329C 420A 319A 319C 503D 262B 410A 409D 409B 158A 405F 404A 405C 332A 135D 405A 158B 145B 409A 503C 503E 106A 120B 145A 406D 249D 249C 610A 610A 406A 282F 405B 329A 262H 103C 135C 402A 402A 410G 406B ...

Page 40: ...FREEZER PARTS CAUTION Use the part number to order part not the position number 40 145C 136A 136B 237C 248F 145F 177B 131A ...

Page 41: ...ber to order part not the position number on some models 41 141B 141C 141A 141B 141C 141A 146A 161E 141B 141C 141A 141B 141C 141A 147C 147B 147A 167B 154A 161A 145E 161C 160B 161A 161D 151A 248H 162B 145D 160B 162A 160C 155J 146B 151C 161F 210A ...

Page 42: ... part number to order part not the position number on some models 42 233A 233D 231A 233B 233C 231B 241C 237A 241C 241C 230B 241A 241B 241C 237A 241C 243A 243A 205C 203A 201A 205B 205A 249B 249A 281D 212D 281D 244E 244E 212G 230A ...

Page 43: ...ICE MAKER PARTS CAUTION Use the part number to order part not the position number 43 602A 600A 616E 619A 623B 623A ...

Page 44: ...P No 3828JL8031C APR 2004 Printed in Korea ...

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