The watch is telling you something
When a mechanical watch misbehaves, it is rarely random. Each symptom — stopping, running fast, fogging, a loose feel — points to a fairly specific cause, and learning the vocabulary lets you diagnose before you panic or pay. Some problems are trivial and self-inflicted; some are free to fix; a few are genuine and urgent. This is a field guide to the common symptoms and what each one means.
It stopped
The most common "problem" is no problem at all: the watch ran out of power. An automatic that stopped overnight simply was not worn enough to stay charged, or was taken off and left longer than its power reserve — wind it 20–30 turns by the crown and reset it. A manual watch that stopped needs winding; if you wound it and it still will not run, that is more serious. If a fully wound watch stops, stutters, or stops only in certain positions, suspect a movement problem — a displaced hairspring, worn parts, or oils that have failed — and see a watchmaker. A watch that stops when laid in one position but runs in another is a classic sign of a service overdue or a mechanical fault, not a quirk to live with.
It runs fast or slow
A watch suddenly gaining time — especially several minutes a day — is magnetized until proven otherwise. This is the most common timing fault, it is harmless, and a watchmaker (or a home demagnetizer) fixes it in seconds; check this before assuming anything worse. A watch running consistently a little fast or slow — a handful of seconds a day — is normal mechanical behavior and can be regulated to run closer if it bothers you. A watch that has gradually drifted from good timekeeping to poor, or whose rate has become erratic, is usually signaling that its oils are failing and a service is due. The pattern matters: sudden and large suggests magnetism; gradual and worsening suggests lubrication; erratic and position-dependent suggests a mechanical fault.
Mechanical watches are not quartz. A typical good movement runs within roughly -5 to +15 seconds a day; a chronometer-certified one is held to a tighter standard. Judging accuracy means measuring over several days of normal wear, not comparing to your phone over an hour — and remembering that how you store the watch overnight (dial up, crown up) measurably affects the daily rate. A few seconds a day is health, not a fault.
It fogged or has moisture inside
Condensation under the crystal is the one symptom that is always urgent. It means water vapor has entered the case, and where vapor goes, corrosion follows — rust on steel parts and dial can begin within days. Act immediately: get the watch to a watchmaker to be opened, dried, and resealed before the moisture attacks the movement. The usual causes are a failed gasket, an unseated crown, or heat-driven ingress; whatever the source, the seal needs attention and the case needs drying now, not at the next scheduled service. Moisture is the rare watch problem where waiting genuinely costs you the watch.
It feels loose, gritty, or wrong
Tactile symptoms are diagnostic too. A crown that feels gritty winding, or a setting action with play or backlash, points to wear in the keyless works. A rotor you can hear clattering loosely in an automatic may have a worn bearing. A bezel that has lost its clicks or a chronograph pusher that feels mushy or sticks indicates the relevant mechanism needs attention. None of these is an emergency, but each is the watch reporting wear, and each is worth mentioning to a watchmaker at the next service. The general rule: a change in how a watch feels to operate is as real a signal as a change in how it keeps time.
Learn the small vocabulary and a misbehaving watch becomes legible: stopped usually means unwound, sudden fast means magnetized, gradual drift means service due, and fog means act today. Most symptoms are minor or free to fix; a few are urgent. Knowing which is which is the difference between a thirty-second reset, a free demagnetization, and a watch quietly rusting from the inside — and it is entirely learnable.