SUMMARY: A LG refrigerator is occasionally unwilling to chill the refrigerator for lengthy periods. I've twice confirmed this by putting a bowl of hot water in it and observing temperatures over the next few hours. Other than this, the whole unit seems to work as expected.
DETAILS: I have a five year old LG LFXS30766S. It's a French-door model, so The top half is the refrigerator part.
After many hours, the refrigerator part will stabilize at just below 37. But in the face of a significant cooling need, such as after opening the door for a while when loading food or adding something warm, the unit simply stops cooling for a long time.
I just did an experiment. I have the unit empty of everything--no food, no shelves, no drawers, nothing. I let it the refrigerator run until it stabilized on the set point for several hours. (See very bottom for how I measure temperatures.)
I heated six cups of water to 180 F. I put that water into a metal mixing bowl. I then placed that hot-water bowl on the bottom of the refrigerator.
WHAT SHOULD HAPPEN: The unit should sense high temperature in the refrigerator, and the cooling mechanism should start and run continuously (except for brief defrost cycles) until the refrigerator returns to the set point.
WHAT ACTUALLY HAPPENS: The refrigerator simply stops cooling for a long time. After I set the 180 F bowl of water in the refrigerator, I monitored temperatures every 15 minutes for two hours. What I measured or observed:
The interior, measured at the bottom, gradually heated from 36.7 degrees to 45.1 degrees. This is unacceptable: since the measurement was at the bottom, upper portions were far warmer (heat rises).
The upper vent temperature started out at 27.1 degrees (the cooling mechanism was running when I started the experiment) and steadily rose. Starting at 45 minutes and through 120 minutes, the upper vent temperature ranged from 52.6 to 59 degrees every time I did my fifteen-minute check.
(reinforcing the prior point) When I started the experiment, the cooling mechanism was on. The circulation fan was blowing, and I could hear the customary sound of refrigerant moving through an evaporator. I briefly opened the refrigerator twice during the experiment--once just after one hour and one at the end. Both times, neither the fan nor the evaporator-gurgling were audible. (The circulation fan is the one behind the rear panel, not the "smell-good" fan at top.)
This clearly means the refrigerator's cooling system never activated for the entire two hours, when it was needed the most!
I stopped the experiment at 120 minutes because I needed to move on. The refrigerator's cooling mechanism had not activated by that time.
I opened the refrigerator at three points: at the beginning of the experiment, a little after the halfway point, and at the end, to remove the warm-water bowl. The only time the cooling mechanism was running was at the beginning, right when I set the heated-water bowl in the bottom. I know it was running both because of the vent temperature described above and because of the customary sound of refrigerant as it moves through an evaporator.
At the end, when I removed the bowl, there was sweat on a glass of water on the bottom (see below for why that was in there).
Prior warranty repairs, in response to this issue, have resulted in two main-board replacements and a compressor replacement. The latest main-board replacement was only around four months ago. This problem has been going on for the life of the refrigerator.
The essential cooling mechanism seems sound. The compressor hums nicely, making no weird noises. When the cooling is actually activated, it seems to do its job.
The freezer temperature is fine (checked sporadically, but never been observed out of bounds, and no evidence of thawing). I am also guessing that an improper freezer temperature would cause ice in the refrigerator door to melt, as it appears cold air is directly piped from there to the door?
The valve controlling flow of refrigerant to the upper vs. lower evaporator is probably not the issue. If it was inadvertently restricting refrigerant flow to the upper evaporator, then the upper circulation fan would be blowing hot air. I've never observed that. When the upper part is too warm, its cooling mechanism is simply inactive.
I get no error codes or beeps. Yes, I've held down those two buttons on the front to get error codes. All it does is activate all LEDs on the front panel. (I do get beeps if a door is open too long.)
It seems something is simply barring activation of the refrigerator's cooling unit when it is needed the most.
I measure refrigerator temperature with a digital probe immersed in a glass that has about a cup of water. The glass is set on the bottom of the refrigerator. The hot-water bowl was set about one foot away from the glass. I have a separate digital probe stuck inside the vent at top, so it can give me an indication of when the cooling mechanism is active. When it is, I will read a cooler temperature than the main refrigerator space. Earlier, that vent temperature was around 27 degrees when the cooling mechanism was maintaining the set point.
I am right now running almost the same experiment on a ~16 year old Amana (Maytag) bottom freezer. I am 75 minutes into it, and it is holding at the set point. (The Amana has shelves/drawers installed and a moderate amount of food, but I don't think either are significant given my experiment design.)
UPDATES: The Amana held its set point very well.
I re-ran the test on the LG and produced very similar results results. Major findings:
- Refrigerator temperature increased and then stabilized at 50-52 degrees between 0.75 hrs and 3.25 hours after I placed the hot-water bowl in the refrigerator.
- The cooling mechanism was only observed at the 0.75 hour and 1 hour checkpoints and again constantly on starting at the 2.75 hour checkpoint. That means there was at least a 1.75 hour period (between 1.0 hours and 2.75 hours) where the cooling system was off even though the refrigerator was far above its set point.
- The starting point was 43.3 F. That is much higher than last night's start point, even though the unit stayed shut for at least 10 hours before then! I stopped taking readings 4.25 hours into this, and the interior temperature was 41.6 F, still about 4 degrees higher than yesterday's start point.
- Between hours 2.75 and 4.25, I suspect the cooling mechanism was running constantly, and it brought the interior temperature down from 52.2 F to 41.6 F. Is that expected for 1.5 hours of running continuously?