Introduction

If your LG refrigerator runs but won’t cool, the fault is usually in airflow (evaporator fan, damper), defrost (heater or sensors), the control board, or the sealed system (compressor or refrigerant). This guide walks through checking whether the fridge section, freezer section, or both are warm, inspecting the evaporators and fans, using the control board test modes, and spotting common frost and temperature patterns that point to the real failure.

What you need

Step 1 Prepare safely

Unplug the refrigerator before removing any panels or touching wiring.
Wear work gloves, and watch for sharp sheet-metal edges behind the rear access cover.
Keep hands and tools off the control board while the unit is plugged in, because you can get shocked.
Use a container to hold screws so none get lost during reassembly.

Step 2 Identify which compartment isn’t cooling

Decide whether the refrigerator section is warm, the freezer section is warm, or both are warm.
Use this checklist to pick a diagnosis path.
Fridge warm but freezer cold points to an airflow issue in the fresh-food section, such as an evaporator fan, wiring, sensor, or damper problem.
Freezer warm points to a freezer evaporator airflow or defrost issue, or a sealed system problem.
Both warm often points to a condenser fan or dirty condenser coils, a control board problem, or a sealed system problem.

Step 3 Access the refrigerator evaporator area

Remove the shelves from the refrigerator section to clear access to the rear evaporator cover.
Pull off any small screw covers, and remove the screws securing the evaporator panel.
Expect two screws behind covers, plus one to two screws on the evaporator plate, depending on the model.
Pull the evaporator panel away once all screws are removed, and let it pop free.
If the panel won’t come off due to ice, run forced defrost or unplug the unit and remove the ice by another method.

Step 4 Inspect the evaporator fan, wiring, and connectors

Inspect the evaporator area for the fan, sensors, wire clusters, and any connectors hidden behind the panel.
Disconnect any wiring needed to fully remove the panel, and keep track of where each connector goes.
Check for wires that are out of place, unplugged, damaged, or pulled tight.
Check behind wire bundles and connectors for moisture damage before plugging anything back in.

Step 5 Evaluate frost patterns and the defrost system

Look at the evaporator frost pattern to decide whether the problem is cooling, low refrigerant, or defrost.
A normal evaporator typically has a light coat of frost across it.
No frost suggests the system isn’t cooling that cabinet at all.
A heavy frost build-up across the evaporator suggests a defrost system problem that needs repair.
A very heavy frost pattern concentrated where the silver lines enter can suggest a low refrigerant condition.
If ice buildup is present, use a multimeter to check the defrost heater and any defrost sensors or thermistors for being out of spec.

Step 6 Test the evaporator fan with the door open

Don’t assume the evaporator fan is good just because it’s plugged in, because these fans shut off when the door is open.
Use magnets on both door hinges to trigger the reed switches and command the fans to run with the door open.
Use a cellphone camera inside the compartment with the doors shut to confirm the lights turn off and the fan starts after about 30 to 45 seconds.
Use control board test mode 1 to force the unit to run the fans if the model supports it.
If the fan never runs under these conditions, the evaporator fan circuit has failed and the fan may need replacement.

Step 7 Access the freezer evaporator area

Remove the freezer drawer door to access the rear evaporator cover.
Use a Phillips screwdriver to remove the two Phillips screws, one on each side of the door.
Lift up on the front of the door to release it and pull it out.
Remove the rear evaporator panel by releasing its tabs or removing its screws, depending on the model.
Remove any rail glides or sliders blocking the panel, and note that some models only require removing the left-side slider.
Disconnect wiring as needed, and remove the cover to view the evaporator assembly.

Step 8 Inspect the freezer evaporator, fan, and defrost components

Inspect the freezer evaporator for light frost, heavy frost, or ice concentrated in one area.
Test the freezer evaporator fan for proper airflow and operation using the same door-switch or test-mode methods.
Use a multimeter to check freezer sensors with the correct resistance chart for the freezer compartment, because values can differ from the fresh-food cabinet.
If there is a lot of ice on the evaporator, test the defrost heater and sensors individually and replace whatever tests bad.
Don’t force off any crossbars or covers until you confirm no refrigerant line is hidden behind them.

Step 9 Inspect the condenser fan and clean the condenser coils

Pull the refrigerator out enough to work behind it, and remove the rear lower access plate.
Use a Phillips screwdriver to remove the six to eight screws, and lift the plate up and off.
Locate the compressor, the condenser coils, and the condenser fan.
Make sure the condenser fan runs unless the unit is in defrost, and clear any obstruction or replace the fan if it won’t run.
Clean clogged condenser coils using a condenser brush, or use an air compressor and a vacuum to remove dirt.

Step 10 Check the control board fuses

Remove the control board cover above the compressor area.
Use a Phillips screwdriver to remove the three screws securing the cover.
Locate any fuses on the control board, because a blown fuse can stop all cooling without showing an error code.
Use a multimeter in ohms or continuity mode to test across each fuse.
Treat the control board area as live whenever the unit is plugged in, because touching the board can shock you.
A good fuse reads about 0.01 ohms, and any result other than OL indicates continuity.
If a fuse is bad, it may be replaceable, but some repairs require soldering or replacing the control board.

Step 11 Run test mode 1 and check for blink codes

Unplug the refrigerator for 30 seconds, plug it back in, and wait about one minute for it to boot.
Locate the test button on the control board and press it once for about half a second until it beeps once.
Confirm the front display indicates test mode 1.
Watch the evaporator fans, the condenser fan, and listen for the compressor while the unit is forced to run.
Touch the compressor and feel for vibration to confirm it is running.
Look for a flashing LED on the control board or front panel, and count blinks to identify fault codes from one to eight.
Turn off room lights if needed, because the board LED can be hard to see.
Codes one, four, six, seven, and eight usually indicate a bad PCB or a loose wire, while codes two, three, and five indicate a sealed system issue or bad compressor.

Step 12 Use test mode 2 to isolate freezer and damper behavior

Press the test button a second time to enter test mode 2.
Use this mode to close the damper and run the freezer portion while keeping the compressor running.
Listen and look for freezer fan operation while test mode 2 is displayed on the front interface.

Step 13 Run forced defrost and reset the refrigerator

Press the test button a third time to enter forced defrost mode, which may display 33 on some models.
Listen for sizzling or crackling as ice melts, because a working defrost system will heat and clear frost from the cabinets.
Let forced defrost run for about 15 minutes, or press the test button again to return the panel to normal running state.
Verify the compressor and fans resume running when the refrigerator returns to normal mode.
Use the power cycle and test-mode reset as a quick attempt to restore operation, even though it isn’t guaranteed to fix the root cause.

Step 14 Test compressor control voltage at CON201

Locate the wire cluster labeled CON201 on the control board near the large capacitor and heat sinks.
Enter test mode 1, and wait 15 to 30 seconds for the system to start commanding the compressor.
Set a multimeter to AC voltage, and probe the two rightmost CON201 terminals that have outgoing wires.
This test is dangerous, so keep fingers behind the probe guards and avoid touching the control board.
Expect about 160 to 185 volts AC while running, and treat readings well above or below this range as a major problem.
If voltage is below 120 volts AC, suspect a control board problem.
Don’t rely on wire color matching between CON201 and the compressor, because it can vary by model.

Step 15 Check compressor current draw with an amp clamp

Keep the refrigerator in test mode while checking current draw.
Set the meter to an amperage range such as 2 to 20 amps, and clamp around one wire feeding the compressor.
Clamp on a single wire, not both wires together, or the reading won’t be meaningful.
If the compressor is vibrating and running, expect a reading around 0.5 to 0.7 on the meter during this test.
If the reading is significantly above or below that range, suspect a low refrigerant condition or a system that isn’t operating correctly.

Step 16 Use coil and line temperatures to spot sealed system problems

Measure temperatures at the silver discharge line leaving the compressor, the condenser coil, and the copper suction line returning to the compressor.
In a working system, the discharge line and condenser coil should be warmer than room temperature, while the suction line should be cooler than room temperature.
Look for roughly a 20 °F difference between the condenser coil area and the ambient air around the refrigerator.
If all three locations are about the same temperature, suspect no refrigerant in the system or a compressor that isn’t cycling refrigerant.
Stop DIY diagnosis here if you suspect a sealed system failure, because repairs are typically beyond a safe DIY fix.

Step 17 Decide whether to repair, replace parts, or call for service

Treat a non-working test mode, abnormal CON201 voltage, or PCB-related blink codes as strong evidence of a control board or wiring fault.
Treat weak cooling with a questionable frost pattern and low condenser heat as warning signs of low refrigerant or compressor trouble.
Check the refrigerator nameplate for the model and serial number, because the first serial digit indicates the year and the next two digits indicate the month.
If a sealed system or compressor issue is suspected, contact LG about warranty coverage, because compressor and sealed system repairs typically require an authorized technician.
Ask the technician what parts they will replace, including the compressor and filter dryer, and how they will address the condensing system and leak checking.

Conclusion

If the evaporators show heavy frost, focus on the defrost heater and sensors. If there is no frost and the coil temperatures don’t show a hot condenser and cool suction line, suspect a sealed system or compressor issue and consider warranty or professional service. Take your e-waste to an R2 or e-Stewards certified recycler. Repair didn't go as planned? Ask our Answers community for help.