My watch is running fast – is it faulty? – Sternglas Help Center

If your watch is running fast, that doesn't automatically mean it's defective. Certain rate deviations are technically inherent and completely normal, especially with mechanical automatic watches.

Why does an automatic watch run fast?

Unlike a quartz watch, an automatic watch is driven by a mechanical movement. Many very small components work together here – with no battery or electronic timekeeping at all.

That's why a mechanical watch doesn't keep time down to the exact second. How much it runs fast or slow can be influenced by, among other things:

Your personal wearing habits
the daily wearing time
the wind state of the movement
the position in which the watch is stored
temperature differences
knocks or strong shocks
magnetic fields

A slightly different rate deviation from day to day is therefore generally normal for an automatic watch.

What rate deviation is normal for my STERNGLAS automatic watch?

The permissible rate deviation depends on the movement fitted.

According to the manufacturer, the following tolerance ranges apply to the automatic movements we use:

Miyota 8215, 821A and 8315: approximately -20 to +40 seconds per day
Miyota 6T15: approximately -20 to +40 seconds per day
Seiko TMI NH35: approximately -20 to +40 seconds per day
Miyota 9015: approximately -10 to +30 seconds per day

This means, for example: if a watch with a Miyota 8215 runs 20 seconds fast per day, it is within the tolerance specified by the manufacturer.

A mechanical watch therefore cannot be compared to the accuracy of a battery-powered quartz watch.

How do I measure the rate deviation correctly?

So that we can assess how accurately your watch is actually running, we recommend observing the deviation over several days.

Here's the best way to go about it:

Set your watch as precisely as possible to a reliable reference time.
Then wear the watch as usual.
After around 24 hours, compare the displayed time with the same reference time again.
Make a note of the deviation.
Ideally, repeat the measurement over several days.

This gives you a much more meaningful result than a single measurement.

Example:
If your watch runs 15 seconds fast after 24 hours, the rate deviation is approximately +15 seconds per day.

Why does the rate deviation change depending on wearing habits?

The rate performance of a mechanical watch can change depending on how often and how long it's worn.

The position in which you store your watch overnight can also have an effect. Depending on whether it's lying, for example:

with the dial facing up,
with the dial facing down,
with the crown facing up, or
with the crown facing down

the movement may run slightly differently.

This means it's possible that your watch won't show exactly the same rate deviation on different days.

My watch is suddenly running noticeably faster – what could be the cause?

If the rate performance suddenly changes significantly and your watch is running noticeably faster than before, magnetisation could be one of the causes.

In everyday life, mechanical watches repeatedly come into contact with magnetic fields. These can come from objects such as:

smartphones and their accessories
tablets and laptops
speakers and headphones
magnetic clasps on bags or jewellery
induction hobs
chargers or other electronic devices

If a component of the movement becomes magnetised, this can affect its rate performance. A typical sign of this is the watch suddenly running unusually fast.

Magnetisation can usually be checked and, if necessary, corrected without much difficulty.

Does a one-off large time difference automatically mean a defect?

No.

Before assessing the rate deviation, you should make sure the watch is sufficiently wound and observe it under normal conditions for several days.

Especially if an automatic watch hasn't been worn for a while or was close to stopping, a single measurement isn't very meaningful.

Can my automatic watch be regulated?

Yes. A mechanical movement can be regulated within certain limits.

This involves fine-tuning the movement's rate performance. However, whether regulation makes sense or is necessary can only be assessed once the actual daily rate deviation is known.

Important: even after regulation, a mechanical watch won't permanently keep time down to the exact second like a quartz watch. Minor deviations are inherent to a mechanical movement due to its design.

When should I contact our customer service?

Please get in touch with us if:

the daily deviation is clearly outside the specified manufacturer tolerance,
the rate performance has suddenly changed significantly,
your watch runs several minutes fast within a short period of time,
you suspect magnetisation,
or the rate performance is very irregular despite sufficient winding.

It's best to observe the watch for a few days beforehand and let us know the following information:

the exact model of your watch
your order number, if available
the measured deviation in seconds or minutes per 24 hours
how many days you measured the deviation over
whether the rate performance changed suddenly
whether the watch may have been exposed to strong magnetic fields or shocks

With this information, we can already get a much better idea of whether your watch is within the normal tolerance or whether regulation or a technical inspection makes sense.