Why Is My Automatic Watch Losing Time?

A mechanical watch running slow is rarely broken. In the overwhelming majority of cases it is one of three things, and two of them cost nothing to fix. The mistake people make is jumping straight to “it needs a service” — the most expensive possible answer, and usually the wrong one.

Work through these in order. Do not skip ahead, because each step rules out a cause and the cheap causes are far more likely than the expensive one.

Step 1: is it actually wound?

This is the answer most of the time, and it is the least intuitive one, because the watch appears to be running perfectly well.

A mainspring does not deliver constant force. It is strongest when fully wound and weakest as it unwinds, and the last hours of a power reserve are where a movement’s rate falls off noticeably. Seiko publishes roughly 41 hours of reserve for its common 4R calibers — but a watch worn only for a working day, then left overnight, may never get near full wind. It lives permanently in the weak part of its reserve, and it runs slow as a result.

The test. Hand-wind the watch 20 to 30 turns at the crown, wear it normally for two days, and compare. If the drift shrinks dramatically, this was your problem. If the movement does not hand-wind, wear it more or park it on a winder for a day and repeat the test.

A related and very common case: desk-diver syndrome. Automatic winding depends on wrist motion, and a job spent typing produces very little. Someone at a keyboard all day genuinely may not wind their watch adequately by wearing it, which is one of the few honest arguments for owning a winder.

Step 2: is it magnetized?

The second most common cause and the most dramatic. A magnetized hairspring’s coils stick to each other, shortening the spring’s effective length — which usually makes a watch run fast, sometimes by minutes a day, but can produce erratic behavior in either direction.

Modern life is full of magnets: laptop lids and their closure sensors, speakers, headphones, tablet covers, handbag clasps, induction hobs, and the magnetic mounts people stick phones to. None of them is exotic and any of them is enough.

The tell is a sudden change. A watch that was running within a few seconds a day and is now minutes out has almost certainly been magnetized. A watch that has always run twenty seconds slow has not — that is just its rate.

The fix is quick and cheap: a watchmaker passes it through a demagnetizer, a process that takes seconds. Many will do it for a nominal fee or nothing. ISO 764 defines a magnetic-resistant watch as one that survives a 4,800 A/m field and still keeps its rate to within 30 seconds a day — if you work around genuinely strong fields, that is the specification to look for in your next watch.

Step 3: what position does it rest in?

Underrated, free, and effective. Gravity affects the balance wheel differently depending on the watch’s orientation, and the difference between the best and worst position on an ordinary movement can be ten or fifteen seconds a day.

A watch spends roughly a third of its life on a bedside table, so the position it rests in overnight has a real influence on its average rate. The practical method:

• If the watch loses time, try resting it crown-up overnight.
• If it gains, try dial-down.
• Change one thing at a time and give each position at least three nights before judging.

This is genuinely how watchmakers regulate to a target rate, and doing it yourself often halves the daily error for the cost of putting the watch down differently. Our accuracy guide covers the underlying mechanics.

Step 4: is it just an unregulated movement?

If the watch is new, runs consistently — the same amount slow every day, not randomly — and none of the above changed anything, the likely answer is that it left the factory unregulated.

This is normal on bought-in movements. Seiko regulates the calibers it fits to its own watches; a micro-brand fitting a Seiko NH35 usually does not. A new NH35 watch running fifteen or twenty seconds a day off is inside the published tolerance for the family and is not a fault.

The fix is regulation, not a service. A watchmaker adjusts the effective length of the balance spring, which is a short job and a modest fee — typically far less than an overhaul. On a consistently-off watch it will usually bring the rate within a few seconds a day.

Step 5: when it really does need a watchmaker

Three signals genuinely point at the movement rather than at any of the above.

An erratic rate

Fast one day, slow the next, with no pattern and no change in how you wear it. Consistent drift is regulation; inconsistent drift suggests something is intermittently binding or that the lubricants have degraded unevenly.

A shortened power reserve

If a watch that used to run 40 hours off the wrist now stops after 20, the mainspring or the barrel is likely the problem. This is a repair, not an adjustment.

It stops while being worn

A fully wound watch that stops on the wrist is not a winding problem. Something is binding — often a knock has displaced something, or dried oil has increased friction past what the mainspring can overcome.

Any of these means a service. Our guide to what a service costs and involves sets out what happens, how often it is genuinely needed, and the price point at which servicing a watch stops being economically sensible.

What is not the problem

Two things worth ruling out because they come up constantly and neither is real.

Overwinding. You cannot overwind an automatic. A slipping bridle on the mainspring barrel means that once the spring is fully wound, further rotation — from the rotor, from your wrist, or from a winder — adds no tension. A watch running slow has too little wind, never too much.

The winder damaged it. There is no mechanism by which a winder makes a watch run slow. The reverse is more plausible — a watch kept on a winder stays near full wind, which is the strong, stable part of the reserve. Our guide on whether winders damage watches handles that question in full.

The short version

1. Hand-wind it 20 to 30 turns and wear it for two days. Most cases end here.
2. If the change was sudden, get it demagnetized. Cheap, quick, and the second most common cause.
3. Change the position it rests in overnight and give it three nights.
4. If it is consistently off but stable, ask a watchmaker to regulate it — a small job, not a service.
5. Only if the rate is erratic, the reserve has shortened, or it stops while worn does it need actual work.