A mechanical watch runs without a battery — through precision mechanics that age over time. The three issues owners meet most often are low power reserve, beat error, and gear wear. They rarely appear overnight; they accumulate.
1. Low power reserve
Sudden stops or a reserve far shorter than before often point here. Automatics left unworn can wind down normally; if the watch is fully wound yet unstable, internals may be at fault: dried oil increasing friction, a tired mainspring, or a less efficient winding system. A full service cleans, lubricates and restores power transfer.
2. Beat error (poise)
On a timegrapher, beat error measures asymmetry in the balance’s swing. Near zero is ideal; excess hurts amplitude and daily rate, and can stop the watch. Impacts that disturb the balance or hairspring, or worn pivots, are common causes. Diagnosis is “invisible” until measured.
3. Gear wear
The wheel train passes energy to the escapement. Poor lubrication, dust or heavy use wears teeth and pivots — first as instability or noise, later as skipping or seizure. Light wear may be corrected by cleaning and oiling; damaged wheels need replacement. That is why a service every 3–5 years matters.
These three often sit on one chain: dry oil → more friction → weaker transmission → amplitude and beat suffer → faster wear. Treat servicing as a check-up, not a last resort.