Automatic Watch Losing Time or Stopping Overnight? How to Diagnose It
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An automatic watch that stops overnight is usually not broken. Nine times out of ten it simply was not wound enough. Here is how to tell the difference between a watch that needs more winding and one that needs a watchmaker.
Why an automatic watch stops at night
An automatic watch stores energy in a spring, the mainspring. A weighted rotor winds it as your wrist moves. The amount of energy it can store is called the power reserve, typically 38 to 42 hours on the movements we use, and up to 80 hours on some modern calibres.
The catch: a quiet day at a desk does not wind the watch much. If you only wear it a few hours, or your movements are small, the spring may only be partly wound when you take it off. The watch then runs out of energy during the night.
The fix: give it a full manual wind. Unscrew the crown if it screws down, then turn it clockwise around 30 to 40 times. If the watch then runs through the night, the problem was simply winding.
Why it loses time when the spring runs low
A mechanical watch keeps its best time when the mainspring is well wound. As the spring runs down, the energy reaching the balance drops and many watches start to lose time in the last hours of the power reserve. If your watch is accurate on the wrist but slow by the morning, that is the likely reason. Wind it fully and the problem usually disappears.
Other causes of losing time
- Position at night. A watch runs at slightly different rates dial up, dial down or on its side. If it loses a little, try leaving it overnight dial up and compare.
- Age and lubrication. Dried or thickened oils slow the movement. If the watch is five or more years past its last service, that is often the answer.
- A shock. A fall can disturb the regulation, so the watch runs slow or erratically afterwards.
When it stops on your wrist
This is different. If the watch stops while you are wearing it, even after a full manual wind, something is wrong mechanically: often the winding system or the mainspring. It needs a watchmaker.
A quick diagnosis in three steps
- Wind it fully by hand (30 to 40 turns) and set the time.
- Leave it still on a table and note how many hours it runs. If it reaches roughly its rated power reserve, the movement is fine and you just need to wear it more or wind it in the morning.
- If it stops well before that, or stops on the wrist, book it in for a service.
Do you need a watch winder?
Not for a watch you wear every day. A winder helps if you rotate several watches and don't want to reset them. For one watch, a full manual wind in the morning does the same job.
Related: automatic watch running fast and how an automatic watch works.