LG LFX25991ST Service Manual

The LG LFX25991ST is a French Door Refrigerator featuring Linear Cooling technology, Door Cooling+, Smart Cooling Plus, Smart Diagnosis, an external water and ice dispenser, and an InstaView Door-in-Door. This service manual provides essential information for qualified technicians, including safety precautions, technical specifications, disassembly/assembly procedures, wiring diagrams, troubleshooting guides, and parts lists. Unauthorized service may void warranty and create safety hazards.

1. Safety Precautions 2. Product Specifications 3. Installation Instructions 4. Component Locations & Diagrams 5. Disassembly & Reassembly Procedures 6. Electrical System & Wiring Diagrams 7. Refrigeration System 8. Control System & Diagnostics 9. Error Code Troubleshooting 10. Parts List & Exploded Views 11. Performance Test Data

Safety Precautions

Before servicing, read all safety instructions. Disconnect power before accessing internal components.

Hazard	Precaution
Electrical Shock	Unplug unit or disconnect circuit breaker. Verify no voltage with meter.
Refrigerant	Use certified recovery equipment. Avoid open flames. Ventilate area.
Sharp Edges	Wear cut-resistant gloves during disassembly.
Heavy Parts	Use proper lifting techniques; two-person lift for doors and compressors.
Moving Parts	Ensure all fans are stopped before servicing.

WARNING! This manual is for trained technicians only. Incorrect repair can cause injury, fire, or further damage.

Product Specifications

Model: LFX25991ST
Type: French Door Refrigerator with Bottom Freezer
Total Capacity: 25.5 cu. ft.
Refrigerant: R-600a (Isobutane)
Electrical: 115 VAC, 60 Hz, 7.5 A
Dimensions (HxWxD): 69.875" x 35.75" x 34.75"
Door Swing: Reversible (default right)
Features: Linear Compressor, Door Cooling+, Smart Diagnosis, InstaView, External Ice/Water Dispenser
Weight: 326 lbs

Installation Instructions

Proper installation ensures performance and longevity.

Location: Level floor, away from heat sources, with adequate ventilation (2" clearance sides/back, 4" top).
Leveling: Adjust front leveling legs for stability and proper door seal.
Water Line: Connect to cold water supply (1/4" copper or plastic tubing). Install shut-off valve.
Electrical: Dedicated 115V, 15A grounded outlet. Do not use extension cord.
Door Alignment: Adjust hinges if doors are not flush or sealing properly.
Initial Power-Up: Allow 24 hours for temperature stabilization before loading food.

CAUTION! Do not install in areas with ambient temperature below 55°F (13°C).

Component Locations & Diagrams

Key internal components for service reference.

Component	Location
Main Control Board (PCB)	Top rear, behind control panel cover
Linear Compressor	Bottom rear, lower compartment
Evaporator Fan Motor (Freezer)	Behind rear panel in freezer compartment
Condenser Fan Motor	Bottom rear, near compressor
Damper Control Motor	Between fresh food and freezer compartments
Ice Maker Assembly	Upper left of freezer compartment
Water Valve Assembly	Bottom rear, behind kick plate
Temperature Sensors	Various locations in both compartments

Disassembly & Reassembly Procedures

Step-by-step guide for accessing major components.

Door Handle Removal: Remove cap covers, unscrew bolts from inside door liner.
Door Panel Removal: Remove hinge covers, disconnect wiring harness (for InstaView), lift door off hinges.
Control Panel Access: Pry off decorative trim, remove screws, disconnect connectors.
Evaporator Cover (Freezer): Remove shelf and rear panel screws.
Compressor Access: Remove rear lower kick plate, disconnect electrical and refrigerant lines (qualified personnel only).
Water Dispenser Assembly: Remove dispenser cover, disconnect tubing and electrical connections.

Note: Document wire and screw locations. Handle glass and plastic parts carefully.

Electrical System & Wiring Diagrams

Circuit diagrams and connector pinouts for diagnosis.

Main PCB Connectors: Power Input (CN701), Compressor (CN703), Fan Motors (CN705, CN706), Sensors (CN708), Display (CN711).

Voltage Checks: Verify 115VAC at input. Main PCB outputs 12VDC and 5VDC for controls.

Grounding: Ensure all ground connections (green/yellow wires) are secure.

Wiring Diagram Reference: See fold-out schematic page S-1. All wire colors and connector codes are listed.

Refrigeration System

Sealed system using R-600a refrigerant.

Compressor: LG Linear Compressor (Part # AJQ72907501). Variable speed control.
Condenser: Serpentine coil, forced air by condenser fan.
Evaporator: Plate-type in freezer compartment.
Capillary Tube: Fixed metering device.
Filter-Drier: Located near compressor.
Charging Amount: 2.3 oz (65g) of R-600a. CRITICAL: Must be weighed in.

WARNING! R-600a is flammable. No brazing on sealed system without proper purging. Use nitrogen when brazing.

Control System & Diagnostics

Using Smart Diagnosis for fault detection.

Enter Diagnostic Mode: Press and hold "Ice Type" and "Temp Down (Freezer)" buttons on control panel for 3 seconds.
Test Functions: Cycle through compressor, fans, heaters, and valves using the "Temp Up/Down" buttons.
Sensor Values: Display shows temperature readings from all sensors in Fahrenheit.
Smart Diagnosis (App): Use LG Smart Diagnosis app with smartphone microphone to receive error code from unit's acoustic signal.

Default Settings: Holding "Freezer" button for 10 seconds resets ice maker.

Error Code Troubleshooting

Error Code	Description	Possible Cause	Action
ER-IF	Freezer Sensor Fault	Open/short circuit in sensor or wiring	Check resistance of sensor (10kΩ @ 77°F). Replace if out of range.
ER-FF	Fresh Food Sensor Fault	Sensor failure	Test sensor. Check connector CN708 on main PCB.
ER-DS	Defrost Sensor Fault	Defrost sensor or heater circuit	Check defrost heater continuity (~20-30Ω). Check defrost thermostat.
ER-CF	Condenser Fan Fault	Fan motor blocked or failed	Check for obstruction. Test fan motor windings.
ER-HG	High Temperature Error	Poor cooling, overcharge, door ajar	Check door seals, compressor operation, refrigerant charge.
ER-SY	Communication Error	Wiring between display and main PCB	Check harness CN711. Replace main or display PCB.

Parts List & Exploded Views

Reference diagrams for part numbers and assembly order.

Door Assembly (Left): Part # MFL68243304
Linear Compressor: Part # AJQ72907501
Main Control Board: Part # EBR77629504
Evaporator Fan Motor: Part # 6325ER2005A
Ice Maker Assembly: Part # 5230JA2006A
Water Inlet Valve: Part # 3855ER1002B
Temperature Sensor (Freezer): Part # 6750ER1002A

Note: Always verify part number with model and serial number before ordering. Exploded view references: Fig. 1 (Cabinet), Fig. 2 (Door), Fig. 3 (Refrigeration System).

Performance Test Data

Expected operating parameters under normal conditions (ambient 70°F, empty cabinet).

Parameter	Expected Value/Range
Fresh Food Compartment Temp	37°F ± 2°F
Freezer Compartment Temp	0°F ± 2°F
Compressor Run Current	0.8 - 1.2 A
Compressor Casing Temperature	130 - 180°F
Evaporator Inlet Temp (Running)	10 - 20°F
Condenser Outlet Temp	15 - 25°F above ambient
Cycle Time	Approx. 20 minutes on, 10 minutes off

Service Support: For technical assistance or parts, contact LG Service at 1-800-243-0000 or visit www.lg.com. Have model and serial number ready.