I've had an LG Artcool hanging in my place for like 3-4 years now. Recently I noticed that when it's running, it started making this low humming sound and the unit on the wall vibrates. It cools the temperature just fine though, no leaks. Is this a sign something's broken or do I just need to clean it?
The first thing to do is remove the front panel of the air conditioner and check if the filter has gotten clogged with dust and debris. A clogged filter forces the fan to strain and creates vibration. At the same time, check whether the unit itself is loose on its fasteners - over a few years the fasteners could have come undone, and then even a working air conditioner will start to vibrate. Try gently shaking the panel when the device is off: if it rattles, tighten the screws.
If the panel and fasteners are fine and the filter is clean, the problem is most likely inside. A low humming often means the compressor has started working under overload - this could be due to the refrigerant lines getting dirty or a refrigerant leak, even if there are no visible leaks. Another possibility is wear on the fan bearings, which develops vibration with age.
At this point, I'd advise against trying to fix it yourself. Call a service center and ask for a diagnostic - the technician will listen to the sound, check the refrigerant pressure, and inspect the compressor. If it's contamination, the system needs flushing; if it's wear, parts need replacing. Don't put it off, because under load the compressor could fail completely, and that gets expensive.
Humming and vibration during normal cooling doesn't necessarily mean something's wrong, but it doesn't just show up out of nowhere either. You should definitely check the filter, though usually cleaning it won't completely solve a vibration problem if it's already pretty noticeable. Our AC started humming about a year ago too - at first we thought it was dust, so we blew everything out, but that only helped about twenty percent. Turned out the wall brackets had come loose, and the unit was literally rattling around.
After that I learned to check the mechanics: look and see if the AC mounting on the wall has come loose - try gently pressing on the casing, and if it moves back and forth, that's your culprit. It's also possible that dirt has built up on the fan inside or the impeller is catching on something somewhere. Sometimes cleaning fixes it, sometimes it needs adjustment.
If the brackets are fine, it's better to call a technician - at three or four years old the unit's at an age where parts can wear out, and it's risky to take it apart yourself without experience. I think a preventive inspection will be cheaper than an emergency repair later.
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