This is a UX431DA, Ryzer 3700U, firmware upgraded to 3.01. I bough this computer online two weeks ago. The fan was running most of the time but quite silent, only the airflow noise. Happy with it. About 5 days ago I was working with the computer and I heard a "click" and now the fan is noisy and annoying, high pitch sound constantly. Really annoying. My office table is cleaned every day, I am careful about that. No dust, and absolutely nothing big enough to damage the fan. The fan should not pick any dirt in a week of use. I used compressed air to blow any hypothetical dirt. Opening the laptop (only a week of use) shows the inside crystal clear. The fan shows no dirt either, spin freely and effortless. Computer performance keeps good, no overheating, just regular thermal throttling when I demand performance for more than a few seconds, as usual in this (poorly refrigerated) model. The fan is just NOISY. Very. I would request a refund under Spanish laws, if this issue is not solved. Please, advice.
I upgraded from BIOS 3.0 to 3.01, as downloaded from ASUS website. This upgrade was days before the sudden whining noise. For my (long) experience, this sounds like a mechanical issue with the fan. As I said, I was making the computer working hard for hours, a sudden "click" sound and then the high pitch noise since. Recordings made with the internal microphones of the laptop (the actual subjective experience is not so bad, the internal microphones are picking a lot of noise). Analyzing the sound, I see harmonics in multiples of ~ 200Hz . Too bad I don't have a recording of the noise (faint and pleasant) of the fan when it was working correctly. Thanks.