My food just stared this today. It's only a few months old and was already in for a service doe to losing 2 minutes a day. I'll take it back again for another warranty service, but this is really odd. Anyone seen it before?

 

I have a moonwatch that does that. It’s one of the first things I want a watch maker to look at. What does the chrono reset button do? Does it even engage?

 

No, does nothing. I can half press it, but it doesn't actuate. Initiall the start stop button didn't work, then after a while it started this behaviour

 

Yup - sounds like we have a similar issue. Although, I have no idea what the problem is.

Let us know if you get any details when you get it serviced.

 

The stem bolt for hammer is either broken or missing. It's a common thing I see in watches and would be repaired during a service. One of the Speedmasters I have in my shop right now came in with the same issue. Here's a video I put together a couple of years ago to show how the start/stop works with the stem bolt for hammer in place, and then with it missing:

Cheers, Al

 

Is that a difficult fix?

 

It depends. If the watch is otherwise fine, and you can find the stem bolt for hammer that is missing, then putting it back in place takes about 10 seconds. However when these break in two (the most common failure) there are two parts of this piece that are floating around inside the movement, and sometimes you have to take the entire movement apart to find both pieces.

Here's the one I just serviced, and the red arrow points to 1/2 of the stem bolt for hammer:



Here is the part removed (1/2 the part that is):



So the very small reduced diameter on the left end of this part goes into a small hole in the main plate of the watch, and as you can see the plate has been damaged:



I cleaned off the raised metal (the main plate is made of brass, and plated so it looks silver coloured) and chanfered the hole, and it works fine.
New stem bolt for hammer is installed:



So how does this break? It's by the reset button getting pushed or knocked when the chronograph is in the running state, so that is something you definitely want to avoid.

Cheers, Al

 

Took another look at this on mine tonight.

To my eyes the stem bolt is in place, but doesn’t appear to be in the correct position to lock when depressing the chrono start.

For the chrono reset there appears to be nothing for the pusher to connect to. Almost like it’s stuck in a depressed position.

Either way - watchmaker fix.

 

The “pusher stem for zero action” is stuck in the depressed position. As you can see this moves the stem bolt for hammer to the side to release the hammer on reset. So the stem bolt is stuck in the reset position.

Not near as common as the stem bolt missing or broken, but I’ve seen this a couple of times. How long since the last service?

 

Embarrassed to say - this has never been serviced.

2012 watch.

 

Time for service anyway then...

 

Looks like the same behavior as holding the reset pusher in while starting the chronograph, then pushing it again to stop... it will immediately reset instead of stopping

 

Nice and informative as always Al, thanks for sharing!

 

Eh, you got your money’s worth. Nothing embarrassing about that.

 

It's more that i've know it's had this issue for several months - (okay a yr) - and i haven't prioritized getting it serviced

 

Yikes. I have read, elsewhere online, that pushing reset while running the chrono is fine. The "video manual" online says to only reset when stopped, so that's a pretty definitive answer.