Why is my Seiko running fast or slow?

This is the most common disappointment in watch ownership and it comes from a mismatch of expectations rather than a mechanical problem. People arrive at a mechanical watch from a phone, which is synchronized to an atomic clock, and from a quartz watch, which is specified in seconds per month. A mechanical Seiko is specified in seconds per day, and the window is wide. The first thing to do is not to search for a repair shop; it is to find out what your caliber is actually rated at.

A watch that has stopped rather than drifted is a different question with a different answer, and it is usually not a fault either: the power reserve guide works through what each caliber's published reserve means once the watch is off your wrist, and why an under-wound automatic looks exactly like a broken one.

What Seiko actually promises, by caliber

Read the second row carefully, because it surprises everyone: Seiko states a narrower accuracy window for the old 7S26 than for the newer 4R36 that replaced it. The 4R36 is the better movement because it hacks and hand-winds, not because it keeps better time on paper. NH35 versus 7S26 and 4R36 versus 6R35 have both sets of datasheet figures in full.

One more thing about those numbers, and it is the part that explains most complaints: a stated rate is measured under defined conditions, not on your wrist. Your watch sees changes of temperature, a variable winding state, and whatever position it spends the night in — and position matters, because a balance wheel behaves differently lying dial-up than standing on its side. A watch that gains 15 seconds a day in the drawer and loses 5 on the wrist is one watch, not two.

How to measure it properly, over a week

Almost every “my Seiko is 40 seconds fast” report is one measurement, taken once, against a clock that may itself be wrong. Do this instead:

• ·Set it against something authoritative. A phone synchronized to network time. Set the seconds exactly if your caliber hacks; if you have a 7S26 it does not, so set the minute hand and note that your measurement carries a few seconds of error. Setting a Seiko has the procedure, including the hours in which you must not change the date.
• ·Wear it normally for seven days. Not in a drawer, not in a winder. The rate you care about is the rate it keeps on you, in the positions you actually put it in.
• ·Compare once, at the end, and divide by seven. That gives you seconds per day. A single-day reading has too much noise in it to mean anything.
• ·Then compare against the row above, not against your phone. If the number is inside Seiko’s window, the watch is working. You can still have it regulated tighter, but that is a preference, not a repair.

The four causes worth checking before you pay anyone

1. Magnetization — by far the most common, and the cheapest to fix

A magnetized hairspring has its coils stick together, which shortens the effective spring and makes the watch run fast— often dramatically so, tens of seconds or minutes a day appearing overnight. The sources are mundane and everywhere: speaker magnets, laptop and tablet lids, magnetic phone mounts, handbag clasps, induction hobs. The fix is a demagnetizer, which any watchmaker has and which costs very little to buy; it takes seconds and does not open the watch. If your Seiko was fine for a year and is suddenly minutes fast, check this before anything else. Seiko publishes a magnetic resistance figure of 4,800 A/mon several references in this registry, including the 5 Sports Field HDB006 and the women’s solar SUP467 — where that row exists it is a genuine specification, and where it does not, assume ordinary susceptibility.

2. Not enough winding — which makes a watch run slow, then stop

An automatic winds from wrist motion, and a desk job with a 41-hour reserve is a marginal combination. As the mainspring runs down the amplitude drops and the rate goes with it, so the classic pattern is a watch that keeps reasonable time all day and loses badly overnight. Hand-wind it 30 to 40 turns in the morning if your caliber allows it — the 4R and 6R families do, the 7S26 does not, which is the single most practical difference between them. Winding a Seiko automatic covers how far to go and when to stop.

3. Position overnight — free, and worth ten seconds a day

Because the rate changes with position, where you leave the watch at night changes the daily average. Try a week dial-up, then a week crown-down, and keep whichever one gets you closer. This is not a trick; it is the same principle a watchmaker uses when regulating, and for a watch that is 10 seconds fast it is often the whole solution.

4. A shock, or a service that is overdue

A hard knock can change the rate by disturbing the balance, and oil that has dried out after a decade will too. If the watch is outside Seiko’s window and it is not magnetized, this is where you are. Regulation — adjusting the balance so the rate sits where you want it inside its natural range — is a cheap bench job; a full service is not. What a Seiko service costs has the intervals and the money.

If the watch is quartz or solar

Different problem entirely. A quartz Seiko stated at ±15 seconds a month that is losing minutes is usually telling you the battery is nearly flat — many Seiko quartz movements move the seconds hand in two-second steps as an end-of-life warning, which is the clearest diagnostic signal in the whole range. A solar Seiko that runs slow or stops is undercharged: it needs daylight, not a drawer, and a few hours on a windowsill will often resolve it. Which Seikos need a battery and which do not sorts the range out, and the solar caliber page has the charge times.

The four watches below are included for one reason each: the tightest mechanical window Seiko publishes in this registry, the movement with the surprising datasheet, the quartz reference whose month-scale rate makes the comparison obvious, and the solar chronograph that never needs a battery at all.