A small home server fan keeps pulsing up and down
A Lenovo M920Q Tiny is being used as an Unraid , with a few Docker services that are mostly idle. The fan is not stuck at a high speed; it repeatedly speeds up for less than a second, slows down for about the same time, and then speeds up again. This does not happen all day.
It mostly appears in the afternoon for about 3 to 6 hours. The happens whether the system is idle or under load. The CPU sits around 43 °C when idle, usually moving only about 2 °C either way, so the looks steady.
The BIOS is already updated to the latest version. Lenovo’s ICE setting was tested in both quieter and cooler modes, but neither changed the fan behavior. The recorded sound was strongly amplified and captured from about 30 cm above the , so the real sound is quieter than the clip suggests.
Key points
- The server is a Lenovo M920Q Tiny running Unraid.
- The fan repeatedly speeds up and slows down in short, steady cycles.
- The issue appears mostly in the afternoon for 3 to 6 hours, not all day.
- The CPU stays near 43 °C, so clear overheating is not shown.
- Updating the BIOS and changing the ICE cooling mode did not help.