If your watch is running very fast, then it most probably will have become magnetised. A watch commonly becomes magnetised through spending too long next to objects that emit strong magnetic fields, such as electrical devices. The most common are laptops, smartphones, domestic appliances and HiFi or mobile speakers.
To test if your watch is indeed magnetised, you can simply take a compass (a digital compass or app on your phone will suffice) and slowly move the watch towards it. If the watch causes the compass needle to move significantly, then your watch is magnetised.
To demagnetise your watch, you need a simple demagnetising tool. Your local watchmaker should have one, or you can purchase your own for around £10/$15.
Here is a quick guide on how to use a demagnetiser:
- Make sure the magnetised watch is not running. Let the power reserve run down and pull the crown out to stop the movement.
- Hold the watch around a centimetre above the smooth pad on the top surface of the demagnetiser.
- Press and hold the button on the device. The light should turn on to let you know it is currently working.
- Whilst holding down the button, slowly lift the watch away from the device until it is 30cm away, then release the button.
- This is one demagnetisation cycle, and you can now test your watch with a compass to see whether or not it is still magnetised. You can repeat steps 1 to 4 until the watch is demagnetised.