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Clock Repair: Analog, 70-78 Z (Round)

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This comes up often enough that it should be posted as a tech article. This is taken from a different posting where Heater Control Panel Illumination was the topic.

In case that is what you were looking for:

(Original Thread: http://www.classiczcars.com/forums/showthread.php?p=141090#post141090)

The Clock not working in the Z's is such an endemic characteristic that it almost seems a basic requirement of the car. If your clock works....it's not a Z.

Fortunately, with a little careful effort it can be avoided. Here's how:

......snipped from original thread....

As far as your clock, you can fix it, and if you're careful it will last a long while. I fixed a pair of these a couple of years ago and they're still working great. I even went the extra step to calibrate it and now it only gains 1-2 minutes a day. Not a chronometer but definitely much better than not working.

Open the clock housing by removing the two screws holding the face bezel in place. Next gently lift off the clock hands, and carefully remove the face. Below it you should find a black washer and a spring tripod washer. Make sure you don't lose these. Once these are off you can address the main problem with the clock.

Added on edit: The sequence of these parts from outside in: Bezel, Minute Hand, Hour Hand, Clock Face, Black Washer, Tripod Washer.)

From the back of the case, ( * see add )remove the 3 nuts that hold the clock mechanism inside the case. Once this is done, carefully force the wire and the rubber boot that powers it, INTO the case, and then do the same thing for the connector. If your connector boot (not the one at the case, but the one where the clock connects to the harness) is pliable enough, gently straighten it out and fold in the heat crimped plastic wings so that it will fit through the hole in the case.

Added on edit: The bracket that holds the clock to the dash and fits the outside of the case needs to be removed first. There is also a "newer" clock version where the 3 nuts holding the clock mechanism aren't on the back of the case and the bracket that attaches to the case and dash doesn't have the extended "handle". Be careful opening these as EVERYTHING inside pops out the minute you remove the bezel.

At this point you should be able to remove the clock mechanism from the metal case.

Take a minute to clean out any dust or gunk inside the case, and if you want it to be brighter when illuminated, paint the inside with a WHITE paint, the green lens on the bulb housing will still illuminate the inside as green, but it will be MUCH brighter when you have the lights on. Be careful not to smear the bulb housing. Set this aside to dry.

Now, looking at the clock mechanism. You'll note a little motor on the back side of the mechanism. ( * see add ) Get a bottle of sewing machine oil and a long enough needle and apply a small drop (by small, I mean minuscule) to the motor housing and the associated pivot points. You can power it up right away, although personally I let this soak for a bit. Usually the length of time to let the paint dry in the case is sufficient, or overnight.

Added on edit: The newer clocks mentioned before have the motor OPEN and with the shaft of the motor being the PENDULUM of the clock. The earlier clocks had a standard clock pendulum but used the motor to WIND the clock spring. The oiling procedures for both are nominally the same.

Next, to ensure that it's working, you can either re-assemble and plug in, or you can provide power to the clock via a 12v power supply. It doesn't require a large current as the motor just winds the spring enough to keep the clock going. If everything is working correctly, you should hear and see the motor wind and you'll notice the pendulum gear begin to oscillate back and forth. I then re-assemble the clock and to ensure it doesn't conk out, I leave it plugged into the power supply for a while.

If you want at this point you could calibrate the clock, except for one thing. Most power supplies supply 12.0v DC, while in the car you will be working with 12.8v to 13.5v depending on the condition of your battery and connections. To get it "perfect" you would need to match the voltage in your car. This takes a l o n g time, so leaving it in the car would be a problem, unless you don't mind having it dangling off on the side for days-weeks. So, if you don't mind it running a bit fast (as mine does), just hook it up to your power supply continuously for a few days.

The procedure is simple.

Once the clock is functioning properly, set the time to match a KNOWN good clock. Whether it's your wrist watch, a house clock, digital or analog it doesn't matter. You're just going to be using it to compare what the car clock is doing in relation to that one.

After 24 hours or thereabouts as it doesn't matter whether you check every 2 hours or 200 hours, compare the time on both pieces. If the car clock shows 12:30 and your reference is 12:00, the car clock is fast, the opposite would be a slow mechanism.

On the back of the clock housing, you'll notice a hole, usually with a milky white plug inserted into it, with markings around it ( + | | | - ).

Added on edit: The newer clock has ( S <----> F ) with the arrow ABOVE the hole while some older models had ( F <----> S ) with the arrow BELOW the hole. The directions are the same, but it's easy to think they're reversed.

Remove the plug, and inserting a small straight screwdriver into this hole, you'll find a screw in there. Give it a gentle twist in the direction you need to adjust the clock. If fast, tweak the screw by a DEGREE or two (360° in a complete revolution) in the - direction. If slow, in the +. Be careful not to over-adjust, a small adjustment of a degree can be as much / little as 10 minutes per 12 hours or less, so by doing small adjustments you won't swing erratically all over the place.

Reset the car clock to coincide with the reference clock. Recheck the two clocks again in another day or so, and repeat the adjustment until they coincide with each other, or you are satisfied with the amount of disparity.

Hope this helps.


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Your timing (ooo, no pun intended) couldn't be better! I sat at my kitchen table not two weeks ago with a screw driver in one hand and my clock in the other wondering how the ^&%&$ I was gonna get my clock to work...Now I have a plan!

PS: are you compiling these tech articles for a book? If not, you should consider it.


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We're pleased to aim! ROFL

Well, it's kind of hard to get people to pay for what I've already given away for free. Heck, in that light, I might have someone looking for me because I gave it away....hmm!!!

The big advantage to having them here is that it draws people to the website. Hopefully they'll buy a CD, T-Shirt, Cap, subscribe to Sport Z magazine or any activity, but you get the drift. That's why I do them here. I used to post at other sites, but not any more.

Can't claim to be another Wick Humble, nor Mark Twain, but hopefully it helps another Z owner to keep his vehicle looking sharp.

Replies such as yours are sometimes all I get, and that makes it worth it.

So THANKS!!! (I don't think there's a "hug" emoticon, and we wouldn't want Bill (Fun in my Z) getting ideas, otherwise LOL consider it here.)


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  • 9 months later...
  • 1 month later...

I did the one out of my parts car today. It's been running for over two and a half hours now, a new record for me and Z clocks!

I took some pictures when I did it, so I thought I'd add them as visual aides. The file names are descriptive.






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How did you go? Did you get it to work? I now have two that have stopped!

Oops, sorry, must have missed this. I had a fairly quick try at getting the clock cover apart, but couldn't. So I tried a spare clock I had and it worked, albeit slowly. Adjusted the speed with the controller on the back and now I have a working clock! It's a smidge too slow, I need to wind it forward about 5 minutes every week. But I'm happy with that.

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  • 2 weeks later...

I was stuffing around with a few Z clocks and found there were mostly two types. The one described above, and the one in my 260Z (a Kanto Seiki). The one I had was driven by a small electric circuit rather than a motor. I couldn't find any schematics so I got the oscilloscope out and traced it out.

Of the three I got working again, one had failed capacitors, one had a failed transistor, and one had both the transistor and capacitor failed. I changed these to equivalents and presto. This was six months ago and they are still going...

I think I will look at a way of putting the circuit, waveforms, diagrams (equivalent transistors will have different pin arrangements), and photos into one document and posting it. It should make a nice little article.

Stay tuned.

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That would be great Monkeyman. I've got one apart in our workshop for about a month now. Tried what you did with the replacing electrolytics and tranny (what sort did you use?), but still didn't seem have have enough grunt to maintain oscillations. I started playing around with a 555 timer setup with limited success. Actually got duty cycle so would drive little pendulum well. Kept time well but after stopped and restarted was real hit and miss and would seem to loose sync and fight itself a bit. I was hoping to be able to build a simple and hopefully more reliable driver that you could exchange the little tansistor oscillator circuit with. Given up for now.

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G'day Maddos,

I like the photo of your zed. Mines the same (except the wheels). I think the metallic blue looks fantastic.

As for the clock, you've noticed the tranny is an 828 (or something that you can't get anymore). I used a BC337. It is just a basic npn BJT we stock at my work. I am sure most common npn BJTs will do the trick. I found that when working, the 828 (or whatever it was) didn't have much grunt and replacing it with the BC337 gave it a bit more. The pin-out is different though! I have started writing up what I did and sketched a pin-out comparison between the two and another common BJT.

You see the little copper-looking metallic disk. It appears to be made up of two windings. From what I gather, one is a 'pick-up'. It detects the magnets on the oscillating disks as they pass. This then creates a pulse, which drives the transistor, which then uses the second coil to give the oscillating disk magnets a little nudge as they pass the coil. Sort of like giving a kid on a swing a push each time they swing past you. I looked at the voltages at the transistor with an oscilloscope and the 828 didn't seem to give much of a push. I don't know if this was a design parameter or if the transistors back then were just junk. The replacement transistor gave it a stronger push and mine has been going strong for over six months now.

Hopefully I will have some sort of write-up in a couple of days to post with pin-outs and waveforms. I will try to make it interesting.

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Yeah I'm a big fan of the blue, plan to have a respray before the end of the year same colour.

Can't remember the tranny I used, but was just a general purpose NPN from tricky ****y. I made sure BEC were configured right but still didn't want to work. That feedback from the coil had me confused on mine, it was hidden under some black goo and didn't know if was supposed to be hooked to pad or not when scraped off for a better look. Anyhow you've got me motivated to re-visit this job. i have a later model clock in my car at the moment out of my parts car but is different look to original and in the guts has a metal can with the workings in it seems reliable

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Take the mechanism out of the can again. Look at the pivot points for the pendulum gear (the one that rotates one way and then the other).

Those should be just shy of being "snug". This is where the "jewels" of the mechanism get used, they are the swivel points.

To loosen the pendulum, in order to have it swing freely that is, you might have to loosen one side or the other very carefully.

You're only going to loosen the screws ~maybe~ a "half-hour's" worth of turn and no more than that (otherwise the axle will fall out of the pivot points and it's not easy to put it back). By a "half-hour" I am referring to the DEGREE's of turn (i.e. 12 hours is one full turn at 360 degrees, one hour = 30 degrees, 1/2 hour = 15 °).

Do first one side, test it, then the other. It shouldn't take more than one or two of these to free up the pendulum.

The purpose of the pivot point adjustment is to both keep it aligned to the pickle fork (don't know the correct name) and to keep just enough pressure on the axle to maintain it in place.

This should free up the mechanism so that it will continue oscillating.

The only other point you might want to look at, is the pickle fork pivot points as well as that you DID get some oil on the motor shaft.

Oiling either the pendulum or the pickle forks shouldn't be necessary as that's what the famous "jewels" are for, but if all else fails, give it a go.



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I worked on mine for several hours before getting it to work reliably. (Still running, BTW.) Enrique's last post is accurate, and is part of what I did to finally get it going. The details of my repair:

  • Oiling the motor - Look at the last picture I posted above. Notice the metal strap across the back of the motor. Slightly loosen the small screw under paint opposite the wires. The wire end of the strap can then be pivotted counter-clockwise to reveal the shaft bushing. Put a small drop of oil there, and immediately blot up any excess. Replace the strap and reapply some lock paint. (Nail polish works well.) Then remove the motor mounting screw (next to my fat thumb in the picture) and the mechanism mounting stud opposite the screw. The motor can then be gently pulled away from the clockworks. Connect 12 volt power and let hte motor spin free for a short while so that you know it works well. Replace the motor.
  • Clockwork pivots - I did not loosen the screws that Enrique mentions, but I did oil (ever so sparingly) all the pivot points. Just like on the motor, apply the smallest drop you can, and immediately blot as much of it back up as you are able.

Doing those two things got mine working well, in fact it might be working too well, as it gains a 2 or 3 minutes per week now. Which is close enough for me.

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  • 3 weeks later...

EScalon, you are my hero! My clock hasn't worked for as long as I can remember, and I decided to buy some sewing machine oil and try to fix my clock following your instructions. Your writeup was very in depth, but pictures would have been alot of help. I didn't quite understand every part of your writeup, but the parts that I did understand did help.

What I decided to do instead was to oil pretty much the whole clock assembly, and let the excess oil run off. I bought a bottle of Singer Machine Oil from JoAnn fabrics today, and used 6 drops out of the whole bottle. I hooked the clock up, while it was disassembled, to my battery charger and watched to see what it would do. I had removed the two screws that hold the motor down to verify that the motor itself was still working, and it spun just fine. I reinstalled the motor, plugged the charger in, and nothing happened. I let the oil soak in for a few more minutes, plugged the charger back in, and then helped spin the gear that the motor presses against. The pendulum started to spin after that, but would stop. I let it sit for a little while longer, went back outside, shook it, and plugged the charger back in. It now works!

Thanks EScalon!

PS: My motor looks a little different than Arne's.


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Try tweaking the pivot points. Sometimes all it takes is one tiny little tweak to release the pressure on that axle, and it will keep running.


Not to seem dense, but I'm kind of lost as what to loosen. I only see one screw, other than the adjustment to speed up/slow down the clock itself. It's running now, but I only let it sit for about 5 minutes. Here's some pics, if you could possibly point out the pivot points and whatnot. The clock ran inside the car for about 5 hours.



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  • 9 months later...

Just noticed Jeremy's post from last August and noticed that nobody had responded to it either.

The pictures you post are both from the FRONT side of the mechanism. They're also too blurry to be able to help you or anyone.

I'll try to describe the screw pivots I'm referring to again:

The Pendulum Gear, the one that runs back and forth, is held in place by two screws which hold the axle of the gear in place.

I've adjusted several of these clocks and it is typically those two screws that are just a little too tight. A very slight loosening is all that is necessary in order to allow that gear to rotate freely. The screw that you use to adjust typically tightens or loosens the spring that the pendulum gear flexes.

If you can post a better picture of both sides of the mechanism, I'll label the points for you.


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Tried this fix on a 71 clock and it started and ran immediately. BUT I was'nt paying attention when I removed the face to its relation to the mounting bracket and cant decide if its on right or 180 degrees out.

Anyone got a picture??:stupid: :stupid: :stupid:

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As you look at the back of the clock housing, the wires coming out will be on the right hand side and the adjusting screw hole will be on top.

Note that this is only for the round clock that has the three mounting studs going through the case and then held on with nuts.


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