VDO Kienzle clock repair

[boxer246]

I realize there is lots of other how-to’s on various forums about clock repair, but I just thought I would write up my experience with my VDO clock repair since it was a fun little father/son afternoon project, and I took a few photos and video and thought I’d pass it along. I found lots of bits of great info in other forums and posts on the subject, but they all seemed to leave a lot out....not implying my write up is seriously more comprehensive, but I’ll try to hit the main points that I hope may help someone wanting a fun little tinker project

I am in no way either a clock repairman, nor an electrical wizard. So I may, or probably will, say something wrong...feel free to correct me and add helpful things, this is all mostly for fun after all so we’ll keep it positive...no Debbie downers about how stupid the dash clock is and how terrible of time it keeps etc etc. I personally think it’s a cool little part of my original dashboard and gauge set so rants about replacing it with a later Quartz type clock, shift light, AFR gauge etc don’t need to chime in Done disclaiming


My car is a ‘70T and honestly I don’t know when Porsche stopped using the VDO Kienzle electro-mechanical clock, but that clock specifically is what this post is about.
My clock never worked during my ownership of the car....going on 10 yrs now. I just thought it would be cool for it to work, regardless of how good of time it keeps. I did not open up the bezel of the clock to clean the plastic or the face, I only dealt with the workings of it in the back.

The white cover is held on with three tiny 5mm nuts, one of which is encapsulated in a little gray tamper “proof” cover. You will have to carefully break off this cover to access that third nut, no way around this. Tamper cover circled in red in photo.




The way these clocks work is actually super simple, however delicate. Basically there is a solenoid that once energized, only momentarily through a set of points attached to a flywheel, rotates that same flywheel maybe 60-90 degrees of rotation, and then for the next few minutes a spring rotates that flywheel back slowly until the points touch again and the process starts over.
On the most basic level, from everything I’ve read, and was the case with mine, the “failure” of these clocks is the soldered fuseable link connection. This isn’t really a failure but rather a design feature...when the solenoid pulls too much amperage/heat for whatever reason, the solder fails and the solenoid no longer receives 12V.

Part of the mystery, that’s more just misinformation, is what causes the electro portion of the clock to pull excessive amperage. Most writing I found suggests that it’s due to “gummed up” or sticky gears/shafts/mechanism of the clock, causing it to draw too much load to operate. This isn’t very true. The electro portion of the clock only momentarily operates the rotation of that one flywheel. And in the direction that flywheel turns during this momentary actuation is opposite of the direction it turns to actually operate the gears of the clock. That flywheel only has two places that have the opportunity to get “gummed” up or create drag. One is the axle (shaft) of that flywheel, and the other is a spring loaded “dog” that drags across the gear that it actuates. It’s unlikely that either point would have sufficient drag to cause an electro overload. So what it seems to me, is the actual points. Over time they get burned ( mine literally were...sooty dirty and black) and eventually fail to make proper contact, thus drawing excessive load and failing the solder joint. Flywheel circled in blue and red arrow points to the points.



So pretty much the drill is to clean everything carefully, dress the points however you see fit, and lube the mechanism, then resolder the fuseable link.
What I did was use, carefully, a can of electronic parts cleaner, a can of compressed air, and Singer sewing machine oil. The gears in my clock were a little dirty, and this process worked well to get it all clean and moving freely. I was very careful with how and what I lubed, I just used a toothpick dipped in the Singer oil to put a tiny drop on all the shaft “bearing” points and on the gears. I did not oil the jeweled bearings of the main timekeeping flywheel (I don’t know what to call it lol) You may choose to oil them, there seems to be varying opinions on the efficacy of oil on a jeweled bearing. But again I’m not a watchmaker or clock repairman so I dunno for sure. I’m sure there is specific oil available that is better suited, I only used Singer oil because that’s what I have, and the Singer repairman says it does not gum up over time like 3in1 oil. There’s other synthetic oils available for sewing machines that’s probably also good. This picture shows the jeweled bearings and the main flywheel:



Now, before even putting 12V back to it or fixing the solder joint, you can check to see how things are moving (especially the main timekeeping flywheel) by simply rotating the winder flywheel (the one with the points) clockwise (looking at it from the clock face) about 60 deg and let it do its thing. If the mechanism isn’t working smoothly you’ve still got cleaning/lubing to do.

Now if it’s working well, time to re-solder the fuseable link.
It’s very small, and in my case there was still a blob of solder attached.
The solder is low temp....I read somewhere it melts at 250 deg F but I don’t know if that true. That kind of solder is a little hard to find, so what I did was take apart a couple of heat activated wire butt connectors, and cut the ring of solder in half, flattened it out and held it with an alligator clip to do the soldering. According to the manufacturer of my butt connectors the solder used in then melts at about 280 deg so that’s close enough for me. I’ll say this...it’s low temp enough that a soon as your soldering gun tip touches it it’s liquid. I used a very tiny bit of flux and that helps it flow.
In this pic you can see the fuseable link apart (before repair) and the blob of solder left on there when it failed:



Here’s the butt connectors I used:




Here’s after the repair:



Since we definitely want the overload protection to be in place, and I’m not 100% sure my low temp solder joint will provide that protection, when I install the clock back in the car I’m going to put a inline fuse on the 12v supply wire. I’ve heard others have done this and I’ve read using anywhere from 1-3amp fuses....I have no clue how much the clock draws when properly working so I’ll start at 1amp and if it blows go up from there.

So that’s about it. My clock when left being tested before I reinstall in the car would lose about 5 min in 24 hrs so I turned the small adjustment screw on the back of the clock I about an 1/8th of a turn towards the + sign and it’s now keeping pretty close time.

I have a short video of the insides while running but I can’t figure out how to upload a video. I’m not really tech savvy if someone knows how let me know.

The clock ticks like any other mechanical clock, and every few minutes the electro points activation can be heard as well. Kind of neat, I think.

[deckard]

timely information. i am getting ready to do my clock as i miss the ticking sound when all is quiet. it will spend about a week to show a twelve hour passage on the face so it works but is bogged down.
i thought at first that the hands were being jostled forward by the vibrations of the car on the road so i set it for 5:30 thinking that if that were true then the hands would stay down but they made there way back up to 12:00 and beyond so there is hope.
i had a watch maker tell me that it would cost $300 to fix it but maybe now i can do better than that. all part of the charm.

[boxer246]

More than likely just needs a good careful clean and lube. Sounds like your solder joint is still intact otherwise it wouldn’t be doing anything.

Also take care not to spray so much electronic contact cleaner in or around the mechanism that it dribbles down inside the clock face area. I would guess it might harm the painted face. I held the clock face up while doing this to avoid that possibility.

[30westrob]

I understand the reason for the low temp fuseable link is if the battery is at a very low state of charge, and does not have enough power to wind, then the contacts remain closed, and overheat the solenoid. The link melts and protects the solenoid.

I like your idea of using but connector solder. Rob

[boxer246]

Rob that’s interesting I hadn’t heard or thought of that. Makes sense.
I’m curious to know how much amperage the thing draws when working correctly. But since it’s just a momentary draw I’m not quite sure how to measure that.

[MikeDL]

https://electronics.stackexchange.com/questions/539887/replacement-for-50-year-old-solder-fuse-technology

I am refurbishing an old automotive clock (VDO Kienzle) that uses an internal low-melting point (~120 degrees F) proprietary solder "fuse". Is there a way to calculate or estimate the size of a suitable modern automotive fuse replacement, specified in amperage?

I don't know if it will be possible to determine at what current the solder fuse "blows." But as a practical matter, you could measure the normal current consumed by the clock, double it, then round up to the nearest standard value fuse.

IMPORTANT: fuses are sized to protect the wire, not the device at the end of the wire. Wire and fuse must be chosen together. And of course, both must be large enough to support the load. Once you fuse the wire, it is OK to use heavier wire. The fuse imposes a minimum size on the wire, not a maximum.

Based on the comment, maybe a thermal fuse would be more appropriate.

It can be tricky to try to protect against a stuck solenoid using a normal over-current fuse. The reason is that you WANT the fuse to blow when the normal operating current happens, but only if it happens for a long time. Unfortunately, if the solenoid gets stuck on, the copper wires will heat up, increasing resistance and reducing the current. This means you need a smallish fuse. But if the fuse is too small it may blow when there is no fault. On the other hand, if it is too big, it may not blow even when there is a fault, because the solenoid current will decline over time. It is kind of like chasing a ball downhill. You try to catch up with it but it goes faster and then you speed up, but by then it speeds up too, and you never catch it. I have been down this road before trying to find the goldilocks fuse.

If the solenoid is accessible it may be better to put a thermal fuse in physical contact (with silicon or something) with it. So the solenoid current goes through a thermal fuse (AKA thermal cutoff or TCO) which physically touches the solenoid. Then if the points stick, and the solenoid starts to heat up, the heat will reliably blow the TCO. TCO's are subjected to a lot of regulatory stuff and are very reliable because of it. Protecting against over-temperature is their one and only job.

There are wide ranges of temperatures available.

See just as an example the NTE8070. (No affiliation or commercial interest on my part and there are other parts out there this is just an example).

[shadowjack1]

Thanks for sharing.

[boxer246]

Yes thanks Mike that’s great information about the thermal fuses. Seems like if that could be soldered easily to the terminals that would be a good alternative. I see in the initial query it says 120F.....but what I read was the solder has a melting point of 120C....roughly 250F I think. If it were 120F the fuse would blow anytime you park the car with the windows up in a southern state in the summertime, the temp can easily exceed 120F inside the cabin.

[Uwon]

Thanks for sharing. I only wished you had also tackled pulling the glass off the front to clean up the face. Maybe somebody will chime in with some good instructions.
Johan

[boxer246]

Johan, I may yet do that, as my hour hand barely touches one of the face screws as it sweeps by every 12 hours and so it really needs to be adjusted.
Removing the bezel isn’t terribly difficult, just fiddly and a little tedious. I think some have made a sort of roller to re-crimp the bezel when reassembling.
If anyone has a picture of a tool like that I’d like to see.

[47silver]

Maybe a jewelers bezel tool would work on rolling the bezels? Cant post a photo from this phone but search for bezel rolling tool. They are in-expensive

[John W.]

Great write up and pictures. Thanks for taking the time to do this.

[doswald]

Boxer246, thank you for the excellent write up. The clock on my '71 seems to be frozen. The fusible link is in place, and the points will open when energized, but nothing moves after the flywheel rotates. I don't see any broken gears. Any ideas? Can you be more specific as to the lubrication points?

Johan, the front of my clock is plastic, although my other gauges are glass. Accordingly, it doesn't polish up as glass would. There are several posts regarding removal of the gauge bezels. Basically, carefully pry the edges of the bezel with a small screwdriver or pick until it can be removed. Reinstall by carefully crimping the edges. Any minor damage can be touched up with a Sharpie and will be hidden by the rubber gasket holding the clock in the dash.

dho

[boxer246]

Doswald…..I can’t say for sure where your problem lies, but my guess is that the little tiny “yoke” that flips back and forth to rotate the thin sharp toothed plastic gear, is stuck. But that’s just a guess it really could be just a little sticky everywhere.
Have you started by cleaning everything yet?
The lube points that I did were: every axle of every gear, wherever that axle rides in its pivot point. But perhaps refrain from lubing the jeweled bearings. Although that remains up for debate. The gear teeth can also be lubed but maybe just a drop because you don’t want excess lube being “flung” around inside there.
After cleaning and lubing, to check to see if the mechanism will work, you can….VERY gently take your finger, or a pencil eraser and rotate slightly the main timekeeping flywheel against its hair spring, let it spring back and see if that “jumpstarts” things to get moving. If things begin moving, then try rotating the winding flywheel (the one with the points) again to see if that keeps things moving. Obviously be very gentle with whatever you actuate by hand as it’s a delicate mechanism.

[Jay Laifman]

I have a new perspective and possible cause - at least for some of the failed clocks. My '73 clock stopped working a while back. I reattached the blown fuse link using the solder that was still there. Worked fine for a long time. Recently, soon after daylight savings change, it blew again.

I took it out to clean, lube, and do the diode and capacitor modification that is out there. But, in playing with the clock, I noticed the center adjuster knob didn't pop all the way out all the time. Sometimes it pops out all the way. Sometimes it pops out partially. When partially out, the clock can still turn but there is friction, which binds the clock. I must not have noticed this the last time I adjusted the time.

I'm figuring this is exactly what happened to pop that fuse, which is supposed to do exactly that - pop when the clock is under too much friction.

So here's the question to this group. Does anyone know about fixing this?

I dripped some penetrating oil in the back of the little adjuster and it definitely moves more freely now. But it still sometimes doesn't snap all the way back.

I'd take off the bezel and see if there is something I can do. But I hate taking off the bezel trim, and I definitely don't want to bother is there is nothing I can fix in there.

FWIW, I have also asked at the Early911SRegistry and the 912BBS boards and so far, no good answers.

[jbell959]

Originally Posted by Jay Laifman

I have a new perspective and possible cause - at least for some of the failed clocks. My '73 clock stopped working a while back. I reattached the blown fuse link using the solder that was still there. Worked fine for a long time. Recently, soon after daylight savings change, it blew again.

I took it out to clean, lube, and do the diode and capacitor modification that is out there. But, in playing with the clock, I noticed the center adjuster knob didn't pop all the way out all the time. Sometimes it pops out all the way. Sometimes it pops out partially. When partially out, the clock can still turn but there is friction, which binds the clock. I must not have noticed this the last time I adjusted the time.

I'm figuring this is exactly what happened to pop that fuse, which is supposed to do exactly that - pop when the clock is under too much friction.

So here's the question to this group. Does anyone know about fixing this?

I dripped some penetrating oil in the back of the little adjuster and it definitely moves more freely now. But it still sometimes doesn't snap all the way back.

I'd take off the bezel and see if there is something I can do. But I hate taking off the bezel trim, and I definitely don't want to bother is there is nothing I can fix in there.

FWIW, I have also asked at the Early911SRegistry and the 912BBS boards and so far, no good answers.

Most likely you have some corrosion in the stem of the adjuster. You will probably need to remove the tiny pin and take the knurled knob off so you can disassemble and clean everything.

That said, friction on the movement has no bearing on the electrical portion of the Kienzle clocks. Friction may cause the clock to run slow or stop but it has no effect on the current draw. The clock only draws power with the contacts touch and if working correctly just for a brief second to energize the electromagnet.

[Jay Laifman]

Oh, that point about the wrong friction makes a lot of sense. Thanks for the thoughts.

[HerrDoktor]

Sorry to hijack (revive?) an old thread. I dissembled my clock today because it has been buzzing but hands not moving for a couple years now and I am finally starting to address.

It seems one of the cog shafts (I am sure that is not what is called) is broken despite the movement otherwise looking fine and motor running. See the white gear in the image. The shaft closest to the clock face seems to have snapped.

Any suggestion on who to send it to to fix or can I order a replacement part and do myself? I am in NJ but can send anywhere in the US.

[jbell959]

Originally Posted by HerrDoktor

Sorry to hijack (revive?) an old thread. I dissembled my clock today because it has been buzzing but hands not moving for a couple years now and I am finally starting to address.

It seems one of the cog shafts (I am sure that is not what is called) is broken despite the movement otherwise looking fine and motor running. See the white gear in the image. The shaft closest to the clock face seems to have snapped.

Any suggestion on who to send it to to fix or can I order a replacement part and do myself? I am in NJ but can send anywhere in the US.

That is, unfortunately, the issue with the clock you have. That clock movement was only used for a few years, from late 73 to sometime in 77. Almost every clock I take apart has one of two broken gears. Someone was making a replacement gear for the other one that commonly breaks, but I have not seen a replacement for the one that is broken in your clock. These clocks are either plastic-welded or riveted together and not made to be repaired. The process to get them apart and back together is time-consuming.

If the date stamp on your clock isn't important, I'd recommend getting yourself a later 78-on clock. The movement is much better and will last a lot longer. It was changed a couple more times through the years so the later 84-89 clocks are the best, but all the movements are interchangeable and were used in a lot of other clocks.

If you want to keep the original clock, I can check to see if I have a good used movement. I have a box of these movements, most with broken gears. The issue with a good-used movement is that you could end up with a broken gear a month from now.

[HerrDoktor]

Legit response. Thank you!

I'd be happy to replace with a more robust movement regardless of year. I just balked at the $700 replacement I found online. I can ignore a broken clock for $700.

Interestingly the clock was serviced a few years ago in London with John Ostick at jdo1.com via the previous owner. I assumed the movement was replaced at that time. I reached out to John just to cover my bases.

Do you have a later movement I can drop in the case?