Noisy or rubbing rotor on an automatic rep watch: what is normal?

Watches Movements & Tech
1

A question that comes up often without having its own thread: when you shake an automatic watch, you hear the rotor spinning. Sometimes it’s a soft whirr, sometimes a sharper noise. Where is the line between normal and abnormal? And does the display caseback help you judge, or not?

[[PHOTO: Fond transparent d’une montre automatique, rotor visible, montre tenue de côté pour montrer l’espace entre le rotor et la glace du fond]]

Editorial summary, not independently verified.

2

Normal: a whirr or a light whistle when the rotor spins freely. On many movements the rotor winds in one direction only and spins freely in the other; that free direction is louder.
Keep an eye on: a noise that changes from one day to the next.
Not normal: rubbing, scraping or a knock when you turn the watch gently.

3

And rotor play? If you can see it move up and down a little through the display caseback, is that already a defect? Or is a bit of play always there?

4

Mini comparison:

  • Slight play, rotor spinning without touching: common, just keep an eye on it.
  • Rotor touching the caseback: circular marks on the inside of the caseback or on the crystal, rubbing noise. Not normal.
  • Rattling noise when you shake it, even without rotation: something is loose. Not normal.
    In the last two cases, stop wearing the watch and don’t open it yourself.
5

Why not open it? Because a rubbing rotor can come from a loose screw, a worn bearing or a badly fitted caseback, and each cause needs a different fix. That’s a watchmaker’s job; when and how to find one is explained in Servicing a replica watch.

6

And can a knock or a magnet cause this kind of noise? Or does that only affect accuracy?

7

A knock can shift something and cause rubbing; a magnet mostly affects accuracy. Both are covered in Good habits for a rep watch. And on arrival, rotor noise is one of the points to check, along with winding and power reserve: see the arrival check.

8

In short:

  1. Soft whirr when the rotor spins freely: normal, especially in the direction where it doesn’t wind.
  2. Slight play without contact: common, keep an eye on it.
  3. Rubbing, circular marks on the caseback or crystal, rattling: not normal, stop wearing the watch.
  4. Don’t open it yourself: go through a watchmaker.
  5. To compare over time, record a short video with sound on arrival.

Editorial summary, not independently verified.

9

Thanks, the video on arrival is a good idea: it gives you a reference point if the noise changes later.