GMT II time-keeping accurate only when fully wound

[stanima]

I thought my GMT II (16713) was keeping lousy time. I purchased a winder, and since I got it I have been keeping it on the winder when it isn't worn.

So before I got the winder it was losing 3-20 seconds a day. On average a minute every 2 weeks. My normal wear period was 8 hours a day, as I work from home and don't put my watch on until I headed out. That was usually between 2 and 3 pm, and then keep the watch on until bedtime, 11 or midnight.

Since I have been using the winder, exactly one month ago, the watch is exactly 1 second slow. Or 0.032 seconds per day.

My question- is that normal? If the watch is only partially wound will it run slower? I would have thought that with a good mainspring the watch would run the same whether the power reserve was full or nearly depleted.

Watch was fully serviced at the beginning of 2016 by Rick Dietel.

Thanks.

[mobster600]

Maybe you need a new main spring or power transfer mechanism idk the name. Your correct the tension should be the same wether it's near depletion or fully wound. I would say to keep using the winder since it's working and manually wind the crown every once in a while.

[Vanessa CW21]

Your watch seems to be winding properly, so I would not be concerned. It seems to me that your wearing habits just aren't enough to wind the watch to the point were it keeps good time. The mainspring should provide even timing between the fully wound position and the 24h later (about half way down) but after that, the lack of power can affect the timekeeping significantly, as you've noticed.

[ROLLiWORKS]

+2