What causes a watch to run fast? And to what degree?

[Samanator]

From my experience a quick running watch was the result of two factors. One got a kink or stuck coil in the hair spring during shipping that took a while to work out with the watch being run until dead a few times. The second was a very magnetized NOMOS that took a few(7) demag sessions to get it working (those cheap demags on Amazon had no effect on it, it took a expensive commercial unit to bring it back). First time I've had a magnetized watch.

Yours sounds more like a cleaning issue as others have suggested.

[Rdenney]

I'm in a similar boat. My 1950-1960's Ebel Cal 119 (A Schild movement) gains ridiculous amounts of time time (up to an hour a day). Also, it does not hold power; it will run nicely (but v. fast) on my wrist but then stop after about an hour when taken off. Would a tangled balance spring account for the loss of power reserve? Could a mainspring problem (slipping?) account for both running fast and loss of power reserve?

It is back at the repairer's but I would appreciate any suggestions.

There are many possible problems and even multiple problems that are interacting. A proper timing test might expose some. The problem could be too much end shake in the balance staff, pallet fork, or escape wheel. High positional variation would expose this, particularly if the dial-up versus dial-down positions differ a lot in rate or amplitude (they shouldn't).

It could also be a loop of the hairspring caught on the regulator pins or mounting stud, which will reduce amplitude and cause it to run fast. A magnetized hairspring can to the same thing, though slight magnetization that doesn't make two loops stick together can still pull on those loops with the effect of shortening the hairspring during parts of the balance motion.

Note that a shorter hairspring requires more power to maintain amplitude. Power is a function of mainspring size and gearing. Often old watches have tired mainsprings that deliver less power, so amplitude and reserve diminishes.

And then there's the question of whether the auto winder is keeping up. The reverser gears on AS movements can get stuck and not reverse properly--this is related to difficult hand-winding. (Hand-winding on vintage autos that don't disengage the rotor gears during hand winding is always stiffer).

It could be a combination of these. I've had all these issues in various vintage watches.

Rick "thinking a more thorough overhaul may be needed" Denney

[Nokie]

This should give you enough expert advise to make the right decision on the best method of servicing for your watch.

[Der Amf]

This should give you enough expert advise to make the right decision on the best method of servicing for your watch.

Fortunately the decision making process is very simple for me, as I only give myself one option: off its gone to be serviced