[holio cornolio]

So here's an odd one, or maybe not. Maybe a simple one. I have a 6309 7040 which was serviced about a year ago. It's been worn fairly sporadically, but I noticed that the more wrist time it saw, the more accurate it seemed to be. It was running about -10s / day until around christmas when I started using something else as my daily wearer. Anyhow, preferences change and I finally put the 6309 back on a few weeks back. Initially all seemed fine, until I spent a few hours in the car one day, and noticed that the watch had gained about 2 minutes in 4 hours. I reset it and left it on the bedside table over night, when it lost about 30 seconds. Next day was sedentary office day, and time stayed pretty accurate, just gaining about 15 seconds over the working day and settling back overnight. Next day, I went on a bike ride with the kids across some fields and the watch gained about a minute over the course of an hour. so what could it be? Some clues: The more active I am, the more time the watch gains. On sedentary days, it can gain up to about 14 seconds in 12 hours, and lose about 15-30 seconds over night. The more moving i do, the more time it gains, but the overnight loss is fairly consistent. The watch was serviced by a reliable chap, and I trust him. He generally works on much higher end stuff than this, and services a lot of nice vintage swiss stuff. What else? My car is a diesel and I tend to rest my hand on the gearstick, so I figured that maybe vibration is causing the balance amplitude to shorten, thus speeding the watch up, but I have no way to test that. That idea was compounded by the bike ride episode.
What ideas do you have?

 

[Transporter]

Just seconds over 24hrs I'd be more than happy with that, I shouldn't worry yourself too much about that. I'm not quoting anything as I'm 100% sure but I think brietling accept a good few seconds either way over a period of time, my watchmaker told me it once and I was quite shocked at the figure given for the amount of lee way allowed

 

[holio cornolio]

No that part is fine, but it's when I get in my car and it becomes a couple of minutes gained over a few hours that I have a problem with.

 

[7s26b]

Take the back off and wind it up manually to full, then see how it behaves. This will give you a good starting point.

 

[holio cornolio]

Wind manually by spinning the rotor with my finger? Any idea how many rotations would get it to full? Or is there a visual indicator when the mainspring is fully wound?
Cheers
Incidentally, this might also be a red herring, but I used to 'back hack' this watch from time to time. Yesterday I reset the time and gave the hands a full rotation before resetting everything, and today, after a full day in the car (travelling to a customer and back) it's only gained 15 seconds or so. Maybe there was something causing pressure in the gear train? Is back hacking an acceptable thing to do on a 6309????

 

[7s26b]

Here's the tech page for a 7s26, it's very similar to the 6309 - just do the same manual winding procedure.
Do ONE thing at a time, doing more is just confusing the issue at this point.
Usually, if the watch is under wound, it will gain time.

 

[holio cornolio]

Brilliant. Thanks for that. Will give it a go and see what happens.
Cheers

 

[holio cornolio]

So... opened her up and manually wound friday PM and has been keeping great time ever since. I wonder if the mainspring was a bit clagged / sticky, preventing it getting a full wind, but it's gained about 10 seconds over the course of the weekend, which is fine by me. I think I will leave it now, unless is starts to behave oddly again...