A mechanical watch that suddenly stops looks like a fault — but in most cases it is not. The most common causes cost nothing and are settled within a minute. Only after that does it get technical. Work through the following five points in order: they are sorted by frequency, not by drama.
How to work through it
Check the basics: crown and winding
By far the most common cause is no cause at all: the crown is still in its setting position. If it is not pushed back in after setting the hands, the movement stops — on most watches immediately, because the seconds stop engages. So check first that the crown sits flush against the case and, on screw-down crowns, has been tightened again.
The second point is energy. An automatic lives on movement; leave it in a drawer for two days and you will find it stopped — that is design, not failure. Wind it by hand twenty to thirty turns before looking further. Without a tensioned mainspring, every observation that follows is worthless.
Watch the balance: is it swinging at all?
Hold the wound watch to your ear. If you hear an even ticking, the movement is working — then the problem lies with energy or rate, not with the mechanics. If it stays silent, look at the balance through a display back.
If it sits motionless despite a tensioned spring, something is blocking it. A gentle turn of the wrist restarts a healthy balance; if it starts and stops again after a few seconds, that points to low amplitude. That is rarely a breakage and usually an overdue service.
Look back: service history and impacts
When was the watch last with a watchmaker? Oil congeals over the years, friction rises, and at some point the mainspring no longer carries through the full power reserve. A watch that has run ten years without a service and now stops in certain positions is telling you fairly clearly what it needs.
Also think about impacts. A drop onto a hard floor can damage the balance staff even when nothing shows on the outside. If the stopping coincides with such an event, skip the rest of the search and hand the watch in.
Chronograph left running?
On chronographs, look at the stop hand. If the stop function runs permanently it draws noticeable energy from the movement: amplitude falls, power reserve shrinks, and in the worst case the watch stops earlier than it should. A chronograph is made for measuring, not for continuous use — reset it and see whether the behaviour changes.
Check the surroundings: magnetism, cold, moisture
If the watch stops and restarts after a brief shake, a magnetic field may be behind it — the compass test settles that in thirty seconds. Temperature plays a part too: in hard cold the oil thickens, and the watch runs slow or stops until it warms up again.
That leaves moisture. If the crystal fogs from the inside, there is water in the case — and then every hour counts, because corrosion starts immediately. This is the one point on the list where you stop searching and hand the watch in straight away.
What you should never do
- Open the case yourself. Without tools, dust protection and replacement gaskets you cause more damage than you fix.
- Shake a blocked watch until it runs and then keep wearing it — that damages exactly the parts already under strain.
- Apply oil or penetrating spray from the outside. There is no situation in which this helps.
- Simply let a damp watch dry out and wait. Corrosion carries on in the meantime.
- Pull a screw-down crown by force instead of unscrewing it first.
When it has to go to a watchmaker
Three findings end the self-diagnosis: visible moisture under the crystal, a balance that stays still despite a tensioned spring, and stopping immediately after a fall. In all three the problem gets more expensive every day, not cheaper. For everything else you may observe calmly — note over a week when and in which position the watch stops. That note saves the watchmaker half the diagnosis.
Conclusion
Crown, winding, balance, history, surroundings — in that order. The first two steps explain most stopped watches, and both cost nothing but a minute of attention. If it does turn technical, careful observation helps more than any repair attempt at the kitchen table.