The Basics
Temperature settings
Make a point of checking the settings. Someone else may have mistakenly adjusted them. Sometimes, in trying to adjust one setting, we can accidentally reset another.
Food Loading
Too much stuff in the refrigerator can block the vents, often causing items near the vents to freeze; after all, in most refrigerators, the air that cools the fresh food comes from the freezer.
Make sure you pull food away from the refrigerator walls so that the vents are clear and you get good air circulation. Look out for items that can freeze easily (usually these have a high water content like most produce) and locate them further away from the inlet vents (the ones that blow cold air). Your food will stay at a more even temperature, too.
Let's move on to the potential causes.
Causes
The refrigerator monitors the temperature inside the fresh food compartment with a device called a thermistor. A faulty refrigerator thermistor can fool the main control board into cooling your unit's fresh food (refrigerator) section more than is necessary. Most thermistors fail by becoming an open circuit, which will trigger a thermistor error. Occasionally, though, a thermistor's parameters will change and cause the main control board to think things are too hot and start overcooling. You can check the refrigerator thermistor at the connector on the control board.
The resistance of the thermistor is what is monitored by the main control board (more properly, the voltage drop across the thermistor). The control board will sense the temperature incorrectly if the thermistor is out of spec.
- At 20°C (77°F), the resistance is around 10-11kΩ for most LG refrigerator compartment thermistors.
- A quick first check:
- Power down the fridge.
- Then disconnect and reconnect, in turn, each connector on the control board.
- Then try starting the fridge again.
- The thermistor resistance is best checked at the control board connectors. This allows you to "see" what the control board is seeing.
A service manual for your model is the best guide for which connection to check on the board. Here's an example page showing the wires to test for the fresh food (refrigerator) thermistor. This is from a somewhat older LG French door model (LFX25973)
The page states that you must replace the refrigerator if you have an open circuit. Pretty drastic. The problem is that the wiring harness for the thermistor is buried in the insulation of the fridge and cannot be repaired if defective. See below in Additional Information for more on this and other checks to run.
If the thermistor cheks ok, go to the next item.
This is another chief contributor to this condition. If the damper sticks open, the refrigerator will be overcooled every time the freezer cools. This will lead to frozen items as the air circulates and slowly turns the fresh food compartment into a freezer. The damper may be stuck because of ice forming or because the motor has failed
Here is a guide for testing the damper motor on a bottom freezer unit.
- If you have disconnected and reconnected the connectors on the main control board, the thermistor resistance checks ok, and the damper checks ok, monitor the fridge for 24 hours, before continuing.
- If your fridge doesn't have those items, go on to the next item.
On simpler models of LG refrigerators, you may just have a temperature control knob for the fresh food portion that adjusts a thermostat. A faulty thermostat can cause overcooling if it won't open. You can test it by seeing if it opens when placed in a cold environment, preferably close to freezing. If it doesn't open, replace it.
Additional Information
Since thermistors do fail, you should make an extra check at the thermistor location itself, especially if you read an open or a short. You can remove the thermistor from the small cage or grille that holds it. This will allow you to access a pigtail attached to the thermistor. You can then isolate the thermistor and see if the defect is in the thermistor or in the refrigerator's wiring.
If you make this check, you will need to cut the wires to the thermistor. You will then measure the thermistor directly. If it is in spec, but the control panel reading was open, you have an internal wiring problem that will be essentially impossible to fix. The same goes for a correct reading at the thermistor but a short reading at the control panel.
If your thermistor reads shorted or open itself and that matches the control panel reading you got, you may choose to replace the thermistor. You will have to make waterproof splices in the wiring when you connect the new thermistor since it will be subject to moisture.
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