The LFC20770ST is a 20.7 cubic foot French Door refrigerator from LG, featuring a bottom freezer, linear compressor technology, Smart Cooling Plus™ system, Door Cooling+™, LED lighting, external water and ice dispenser, and smart diagnostics. This service manual provides comprehensive information for authorized technicians, including safety procedures, technical specifications, component locations, disassembly instructions, troubleshooting guides, and wiring diagrams.
Before servicing, read all safety warnings. Disconnect power before accessing electrical components. Use proper tools and personal protective equipment (PPE). Handle refrigerant according to EPA regulations.
| Hazard | Precaution |
|---|---|
| Electrical Shock | Unplug unit or disconnect circuit breaker. Verify no voltage with multimeter. |
| Sharp Edges | Wear cut-resistant gloves when handling panels, shelves, or evaporator cover. |
| Refrigerant | Use recovery equipment. Do not vent R-600a (isobutane) to atmosphere. |
| Heavy Components | Use assistance when lifting compressor or condenser assembly. |
| Moving Parts | Ensure fans are stopped before working near evaporator or condenser. |
Key components: Main Control Board, User Interface Board, Linear Compressor, Evaporator Fan Motor, Condenser Fan Motor, Evaporator Coils, Condenser Coils, Water Inlet Valve, Ice Maker Assembly, Damper Assembly, Temperature Sensors.
WARNING! Refer to exploded view diagrams for correct part orientation and fastener locations during reassembly.
Step-by-step guide for accessing major components.
CAUTION! Label all wires and connectors. Note screw lengths and locations.
Circuit includes main control board, user interface, compressor, fans, sensors, and ice maker.
| Component | Location | Test Points |
|---|---|---|
| Main Control Board (PCB) | Rear, machine compartment | Check input voltage (115VAC), low voltage DC outputs. |
| Compressor | Rear bottom | Resistance between terminals: Start (S), Run (R), Common (C). |
| Evaporator Fan Motor | Freezer section, behind cover | Check for 12 VDC supply, fan blade obstruction. |
| Temperature Sensors (Thermistors) | Fresh food & freezer compartments | Resistance varies with temperature (approx. 10kΩ at 77°F). |
| Water Inlet Valve | Rear bottom left | Check for 120 VAC when dispenser is activated. |
Sealed system using R-600a refrigerant. Includes linear compressor, condenser, capillary tube, evaporator, and accumulator.
WARNING! R-600a is flammable. No sparks or open flames. Work in well-ventilated area.
The main control board monitors sensors and controls all functions. Use Smart Diagnosis feature via LG app or manual test mode.
Entering Test Mode: Press and hold "Ice Type" and "Light" buttons on dispenser panel for 3 seconds. Display will show test codes.
Test Functions: Compressor relay, fan motors, defrost heater, ice maker, dispenser lights, valve operation.
| Error Code | Description | Possible Cause | Corrective Action |
|---|---|---|---|
| ER-RS | Refrigerator Sensor Error | Open/short circuit in fresh food thermistor | Check sensor resistance, wiring, replace sensor. |
| ER-FF | Freezer Fan Error | Fan motor failure or blockage | Check fan for obstruction, test motor, replace if faulty. |
| ER-DH | Defrost Heater Error | Heater open or defrost thermostat faulty | Check heater continuity, test defrost thermostat. |
| ER-CF | Communication Failure | Wiring issue between main and display board | Check harness connections, test communication voltage. |
| ER-IF | Ice Maker Function Error | Ice maker motor or sensor failure | Run ice maker test, check for ice jams, replace assembly. |
After service, verify proper operation.
Use genuine LG parts. Reference part numbers from the official list.
Ordering: Contact LG Parts at 1-800-243-0000 or visit www.lgpartsonline.com.
Service Support: For technical assistance, call LG Service at 1-800-243-0000. Reference model LFC20770ST.