Service: Seiko 6309-7040 calibre 6309A

Robert from Sweden sent me three watches for service/repair, and this Seiko is one of them. It’s still ticking, but only barely.

Huge beat error, low amplitude (even for a Seiko), and a very irregular beat rate.

Like a lot of Seiko automatic watches, you can’t manually wind this one. The crown pulled out to the first position sets the day in one direction, and the date in the other. Pulled out to the second position,  you can set the watch.

The luminous compound has attacked the metal of the hands, and they are corroded. I won’t be able to fix that without making the luminous compound come off – I will very slightly slide them over a polishing cloth, but that’s all I can do without having to relume.

The day wheel is Spanish and English.

The bottom plate is fairly complex in its layout, but, as a reward for this complex construction, the date and day change and the quick-set function work extremely well. Watch and learn, Tissot and Omega of the same era!

Everything in good condition. I’m not a huge fan of plastic wheels, but they do the trick.

Having removed the auto-winder assembly, I can take the balance and wheel bridge off. Barrel and wheel bridge are one here, which makes reassembly a bit fiddly. Oddly enough, the third and fourth wheel are not jeweled.

The balance top jewel assembly ready for cleaning.

A simple, but effective click construction. No spokes in the third and fourth wheel, but holes, which are cheaper to manufacture.

Quite a lot of parts for an automatic day/date.

Mainspring greased and the barrel ready for closing.

I start off by putting the balance jewels back together.

Wheel bridge back in and balance swinging.

Now I put together the bottom plate.

I tried to clean up the hands with a polishing cloth, but the damage the luminous compound has done isn’t that easily reversible.

After casing the movement, I put the rotor back on.

This is a lot better than before. The watch isn’t new, and you can tell, but compared to what it looked like before, this isn’t bad. Seiko watches always have a pretty low amplitude, so nothing wrong there. The waves are gone, and I’ve adjusted the beat error.


37 thoughts on “Service: Seiko 6309-7040 calibre 6309A

  1. Hi. I have a 6309 that was repaired a few years back. Within 18 months It ceased working again and has been in a draw since. I’d love to have this repaired and wearable again. Can you do a full restoration and repair on this for me?

  2. I have a ‘vintage’ 6309 divers that “slowed” drastically. I have 2 6309A movements (from Seiko 5 ‘s). Will these fit ‘exactly in the divers or are there differences??

  3. I am curious about setting up the wheels to change the day and date. I know for the ETA 7750 there is a certain way they are installed. There is a score mark on the plate for one wheel and the other has the protrusion pointing toward a pivot. What about this 6309 movement?

  4. Hello
    My name is Patricio, I am writing from Chile,I have a Seiko Divers 6309 and I lost the ring bezel (black) I would like to know if there is a chance to get one and be send it to Chile?.
    The watch is working , and the reason to fix it is that mean a lot to me, and to get this spare part here in Chile is impossible.
    I hope to get a prompt answer


    Patricio Galmez

  5. I’m sorry Christian I have one more question.

    Does a Seiko 6105-8110 wind in both directions on a winder?

    Many thanks.

  6. Can you help? I have a 6309-7049 and a watch winder that rotates clockwise, counter clockwise and both. What is the best direction setting to use? I’ve got a sneaking suspicion that it doesn’t matter.

    Many thanks.

  7. Hello, do you know if there a more modern seiko movement that is hand windable that I could fit into a watch like this? I mean a seiko 6309-7040.

  8. i am looking for a back gasket for a seiko 6309A, 17 jewel auto. the inside dimension is 1.177 In. sae or 29.91 mm metric. I have tried ordering for a 6309a before and the gasket were to large. This is an physical measured actual inside diameter!

  9. Hi,
    I have a Seiko 7c43 that stop working, it seem that the battery has leaked inside and the battery connection spring(+) is damaged (also it seem sticky inside).

    I can’t seem to find a replacements (not to the connection nor to the movement), I really like the watch, is there a solution (like dropping different movement)?

    Thank you,


  10. 🙂 I just opened yesterday a 6309A. Very nice feature: in case you forget which wheel is which: count the holes in them 🙂
    …including the escape wheel, the “fifth one”, it has 5 spokes 😉

  11. I just “won” a mid-70’s Seiko on auction, here’s a pic: and internal view:
    It’s coming from India, sold by the Bombay Watch Studio & is also a 6309a movement. They claim it’s serviced and oiled, and at $29 delivered … I don’t see how it’s sustainable. There must be ways to cut corners on the labor unless this kind of skilled work is really that cheap there. Thanks for the photo essay on this movement, I found it enlightening. I’m tempted to learn more watch repair basics, and I’m headed to the next meeting of the horological guild this week.

  12. Got a spare 6309A for sale? I’ve been trying to look for them for my tuna project but no luck on ebay and other forums. Thanks!

  13. I am the owner of this watch and feel great to see that great care and effort is put into its service. The watch is 35 years old (born on same year and month as myself) and have a special place in my collection and wanted to have it fully functional since I use it on a regular basis. Great work Christian.

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