A 166.010 I recently got had a detached crown. I had thought I managed to fix it, but if I wind it by making the rotor spin, the hands get out of whack. The stem doesn’t seem to engage correctly and trying to wind the watch only moves the hour hand. Letting it run results in the hour hand not lining up properly with the indices.



However, if I remove the stem and replace it, the hands pop back into the right positions. Winding the watch still feels odd, like the stem engages the movement when I turn the crown clockwise, but is in neutral when turning it counter-clockwise. (Checking this with the back off confirms that the stem does engage the movement in both directions, but there’s almost no resistance when turning the crown counterclockwise.)*

* Edit: Every automatic movement I have on hand also behaves this way, so every sentence past the first one in this paragraph can be disregarded.





I realize this is probably not something I can correct at my nonexistent level of skill, but I’m wondering what the origin of the problem is. Is the stem messed up, or did something else go wrong?

 

I think you are describing 2 separate issues. The misalignment of the hour & minute hands would be dependent on either the placement of the hands on their respective pinions, or something badly amiss with the motion works component group under the dial.

The crown & stem coming loose & then not reengaging correctly is a separate issue from the hands alignment, & is most likely related to a problem with the keyless works component group. When you move the crown between winding position & setting position, does it feel like the detent is clicking into position as normal?

Edit: you also say, "if I remove the stem and replace it, the hands pop back into the right positions", but in both photos above with the crown & stem in place the hands look out of position, at least to me. Would be a very strange problem if the hands' relative position changed depending on the presence or absence of the stem. The relative position of the hands is dependent on the gear meshing of the hour wheel, the cannon pinion, & the minute wheel. Something would have to be pretty seriously broken for the gear meshing to slip depending on whether or not the crown & stem are present (not to say that it's impossible, just that it's a strange sounding symptom).

 

Thanks for your response. Everything feels normal when setting the watch, but if I give it a twirl to spin the rotor (i.e. putting it on and calling a traveling foul as a basketball referee), the hands seem to disengage from the mechanism and end up coming to rest wherever momentum took them. Then, setting the hands just doesn’t work—the stem doesn’t seem to engage the gears.

The photos are not super illustrative, but in the second photo the hour hand is in the right position, while in the first it’s way off. Sometimes pulling the stem out to the first or second position corrects this, and sometimes removing the stem completely doesn’t fix it. I’m not any more sure what corrects it than I am what’s causing the problem in the first place.

 

Ya, watchmaker is going to need to open it up & take a look at the keyless works & the motion works under the dial. Beyond saying "something's screwy" (which you already know) would just be guessing.