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VDO Clock Repair

Pelican Technical Article:

VDO Clock Repair

Mack Overman

Applicable Models:

Porsche 911 (1965-89)
Porsche 912 (1965-69)
Porsche 930 Turbo (1976-89)
     I read the article by Demnick Boyden on repairing VDO clocks, with particular emphasis on the solder-fuse repair. The article was excellent and gave me the courage to investigate my problem. You should read his article first.

     The clock in my 67 912 did not work. I removed the three nuts holding the plastic housing, (bezel), on the back of the clock. Two of the plastic seals covering the nuts had been previously removed. I guess that person lost their courage before they got into the clock. I found the electromagnetic disk that rewinds the clock. I loaded it partially with manual rotation. The clock made a couple of ticks and stopped. I rotated the disk further to the fullest stretch of its spring but lack of spring tension was obviously not the problem. The clock appeared to be jammed from all the crusty, dandruff-like buildup of crud all over, and in, the various gear teeth. There is a fragile little open wheel that is spring-loaded, and it rotates back and forth with each tick of the clock. I later learned that this wheel is called the spring balance escape.

     With a gentle flicking of this wheel, the clock made a few more ticks. During this time, I was observing the various directions of travel of the gears, visually working my way backward from the oscillating wheel. The gears closest to this wheel have the lowest gear ratios and are, thus, more easily moveable with light pressure back and forth. Each little jiggle of these gears would produce another series of ticks; each one a little longer in duration. I was getting excited.

     Each series of ticks would also allow the electromagnetic disk to recover progressively from the manually-rotated position to which I had advanced it earlier. As this spring-loaded disk neared the end of its travel, I observed the contact point attached to it and finally saw it come to rest on another contact point. The arrangement looks much like a set of distributor points. The fixed point is on an arm anchored to a rectangular bracket, housing the wound coil that creates the magnetic power. It rewinds the disk when the points make contact. This coil is easily seen since only the back and the two ends of this housing have structure. I noticed the soldered wires at both ends of the coil and assumed this to be the low temp solder to which the warning on the plastic bezel refers. My warning said that my solder thermo-fuse had a fusing point of 90 degrees C or 195 degrees F. There was also a warning that if I removed the sealed bezel back, the warranty would be voided. Oh heck!!

     Well--in any event, the solder connections looked secure. I couldn't be sure because I hadn't applied any 12 volt power to the unit yet. I continued to gently jiggle the mechanism gears and flick the oscillating spring balance escape wheel until the spring-loaded magnetic disk made a complete cycle to points closure with no interruptions. That really excited me. After a few, intermittent, similar successes, I checked the wiring terminals in the car. I had 12 volts to the connectors. What a surprise. Thank you Dr. Porsche.

     With the back still off the clock and with great fear of the unknown, I connected the positive and then the ground wire. VOILA!!! The little points being closed, the wound coil received power, became activated and instantly spun the disk into its spring-loaded, mechanically powered position. The clock started ticking. I don't remember if the clock made a full, unassisted, cycle the first time. Of course, by then, I knew how to jiggle the appropriate gears to free the mechanism. Each time the contact points closed, the electromagnet did a super quick rotation of the disk to reload its spring. When this happens, there is a little sound that will be music to your ears. The sound is a quick, yet soft, click. Then you'll hear the softer ticking of the clock that you heard when you were manually loading the disk. You will wait in great anticipation to see if the clock makes a full, unassisted, cycle. Whatever--- the good news was that the electrical parts, including the dreaded low temperature solder fuses were intact. Afterall, the clock could be cleaned.

     I played with the clock in the car for a little while and then removed it. Back in my study, I continued to exercise the mechanism through approximately 25 cycles of 2 1/2 min duration. All of these cycles were uninterrupted by any stoppages. My plan was to install the clock the next morning with the intention of removing it later for a good professional cleaning when I didn't have so many other pressing priorities.

     My car had been sitting in my garage, untouched, under a cover, for twelve years. The more pressing priorities occupying my time were removing the gas tank, boiling it out to remove rust scale, flushing the steel lines, replacing the rubber gas hoses, disassembling and cleaning the fuel tank sending unit, rebuilding all the brake calipers, installing new brake lines to all four wheels, replacing the front struts and rear shocks, adjusting the valves, installing new points, condenser, plugs, distributor cap, rotor button, treating the cylinders with copious quantities of Marvel Mystery Oil through the spark plug holes prior to spinning the engine, etc.,etc. There were other things, like why I was only getting 9 volts to the positive side of the ignition coil and all of the corroded connections at the fuse block and other places that had to be cleaned. Wait a minute ----- If you're reading this, you probably have a Porsche that's thirty-some years old. Enough said; you understand.

     Back to the clock... I had been fiddling with the clock for about four hours. I must say that it had been great fun, but it was 2:00 a.m. and I decided to get a little sleep before I reinstalled the clock in the car in the morning. I went to bed with a great feeling of accomplishment. When I awoke, I couldn't wait to spin that little disk and hear that beautiful ticking sound. To my dismay and complete consternation, the second such cycle produced a temporary stoppage from crud. A little jiggle restarted it again, but (obviously) the clock had to be cleaned now--before it was reinstalled.

     My favorite little jewelry store could probably clean this clock. I was going there anyway. It was just before Mother's Day. Even though she's not mv mother, my wife is a great mother to our children. And--- she expects and deserves something from me on this occasion. This jewelry store is in its fifth generation of continuous family operation and always has exquisite giftwrap. They all know me and know that I enjoy an occasional bit of humor. They reciprocate accordingly. I walked into the store holding the VDO clock on my wrist. I inquired about the possibility of getting my watch cleaned. Ashley, the pretty, young, female, fifth generation proprietor, responded without missing a beat. No Mack--- we no longer work on Rolexes. Disappointed, but still on a mission, I told Ashley that I needed a little something for Jo, (my wife) for Mothers Day,-- perhaps a pair of earrings. She said she had just the selection for me and that they were on sale! I must admit that she had some pretty earrings, and they were 50% off. Wow, that was great-- but the price was not marked on their tags. I was well into narrowing down my choices when I inquired about their prices. They were all around $700 per pair. Ashley was about to clean my clock afterall, and she hadn't even touched my VDO. I punted and moved into the cheap seats where I was able to procure a lovely pair for one-tenth the cost of the former ones--- and the giftwrapping was, as always, exquisite. Isn't it the thought that counts? Afterall, Porsche parts are expensive and I'm sure that my wife would want that $700 going toward my little project car.

     Once again, back to the clock. It was fifty miles to the nearest-known reputable clock repair shop, so I decided to try cleaning it myself. I figured that if I destroyed it, I could always install one of those VDO clocks with the quartz movement. The clock was making about twenty full cycles without jamming. My thought was that it only needed a little help. The question was "with what cleaner and how"? I decided that an aerosol can with the small straw adapter would give me some pressure-washing like power with good directional control.

     I have used WD40 on electrical parts with some success and I know that it has both solvent and lubricating properties. I sprayed the mechanism, carefully avoiding the wound coil. The    crud was coming off the gears. With great anticipation, I rotated the spring-loaded disk. At that moment, I learned that WD40 is not the thing to use. The clock operated for two or three ticks and stopped. It took lots of jiggling to get it through even one cycle. Apparently, WD40's viscosity is too high for the delicate balance and close-moving tolerances in a clock mechanism. I checked the can label and sure enough--- there was no claim as to the suitability of their product for watch and @lock repair. Oh well! I was sure that I had read it somewhere.

     Instead of jamming once during 5% of it's cycles, it was then jamming throughout 95% of each cycle. My next job was to clean up the mess.

     Perhaps I should use something less viscous that would evaporate more readily. My on-hand choices were carb cleaner, brake parts cleaner and Liquid Wrench. Being concerned for the integrity of the wound coil and other electrical parts, I did not want to use anything stronger than was absolutely necessary. I opted for the Liquid Wrench. I sprayed the mechanism pretty thoroughly and dried it with cotton Q-tips (carefully removing the cotton hairs that snagged on the sharp gear teeth). In each of these sprayings, I held the clock on its side so that the crud and solvent excess would run out of the open mechanism and not into the hard-to-remove face area. I blew gently with only my breath to aid in the evaporation of the solvent. I wanted to get as much of it out as possible before applying 12 volts to the contact points. Afterall, the product does have a "fire and explosion hazard" warning on the can. Notice how I had begun to read labels. The last Q-tipping was done to the contact points which had captured and retained a fair amount of the solvent.

     The moment for the next test had arrived. I manually rotated the disk and it started ticking--and ticking-- and ticking. After many such attempts, it had not jammed even once. I allowed it to air dry for a couple of hours and then hooked it up in the car with the back of the case still off. I watched it operate flawlessly for 15 minutes and, then, left it unattended for the rest of the day. When I returned, it was still working faithfully and had kept perfect time over an eight hour period. I guess I didn't harm it. Maybe I even fixed it. I'll let you know later.

     With a little Friday night and Saturday morning project I had procured a Mother's Day present for my wife and apparently fixed my 35-year-old Porsche clock. Some may think "so what?", but you car restoration buffs who have worked endless hours on a tedious little item, that others might find insignificant, will certainly understand. Not a bad days work!!! It was also great fun. I love to sit quietly in the car, listening to the clock tick. I wait to hear that soft little click when it rewinds the disk. But best of all, with each tick and click that I hear, I know exactly what's going on inside my clock. It just doesn't get much better than that. Keep the faith.

     P.S. As I write this, Its Memorial Day weekend and the clock has been fully installed and working perfectly since Mother's Day. If it stops tomorrow, the fun was worth the effort, but I'd bet that it will serve faithfully for years to come.

Comments and Suggestions:
Ian Wright Comments: Clean the clock works with naptha. Then use watch oil to lube the pivots. Naptha will evaporate very fast. Set the clock works in a dish with a couple of inches of the solvent and agitate it lightly. Be sure not to allow the solvent to go as high as the dial. I use a diabetic syringe for the oil very little is required.
January 1, 2016
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
JPM Comments: The good news is my clock is working again. The bad news is all the mistakes made along the way. I attempted the repair by first removing the outer ring before reading the article by Demick Boyden which would have saved me the trouble since I have a Type I clock. All the solder joints looked fine. I made the mistake of spraying some WD-40 and hooked up to 12v, before reading Demick Boydens bad experience with WD-40. The clock worked for 8 mns then died under too much strain I suppose. I tracked a loose solder joint in a resistor bridging the coil thinking this was the solder-fuse the article talked about but no luck. After rereading Boyden's I managed to resolder the proper connection which had detached as expected but using regular solder since I had no idea where to procure low temp fuse solder. Success at last but an example that impatience leads to mistakes!
May 3, 2015
  Followup from the Pelican Staff: Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
David Comments: Have a VDO clock from my 1991 Grand Banks Motor yacht All my gauges VDO also on the boat The clock stopped working
Can I get soem idea homw much it would cost to repair and where to send it
I live in San Diego Ca there a repair facility here in town
September 26, 2012
  Followup from the Pelican Staff: I would call around the electronic repair shops. I am not familiar with one in your area. - Nick at Pelican Parts  
Don Comments: I am in the process of restoring my 1967 Porsche 912 and the VDO clock is not working. I have verified there is 12 VDC on the spade connector to the back of the clock and there is not any continuity through the clock indicating the original VDO clock is faulty.

However, I cannot loosen the two knurled nuts on the screws that hold the clock in the dash due to the very restricted space and difficulty in accessing the back of the clock from the luggage compartment?
September 15, 2012
  Followup from the Pelican Staff: I would try to grab them using a pair of long needle nose pliers. - Nick at Pelican Parts  
Blaireau Comments: I followed your clock repair story and was able to repair my '63 356B Coupe's clock by merely opening the back and spraying the inside with penetrating oil and allowing it to drip dry for several hours. I used a Q-tip to clean off the contacts and put it on a battery. I'll load a photo showing the clock with the back open and the wire leads attached. My dog can be seen supervising the operation!
Thanks for your thorough and enjoyable post!
December 6, 2010
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
Raymond Blakeman Comments: Electrical tuner cleaner from Radio Shak would probably work better and comes in a presurized spray can. It is a very light viscosity lubricant and cleans plastics and nylon parts quite well if you are unsure clean an old transistor circuit board tuner and observe . I have used it on tacs and speedos on Harleys that I have restored. It works great
May 25, 2010
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
carrerab Comments: I have a porsche 944 with a electrical clock. I want to replace the lcd screen,on the clock. Does any one now how.
November 18, 2009
  Followup from the Pelican Staff: You can get a donor clock and swap them. This thread discusses it: - Nick at Pelican Parts

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Page last updated: Fri 2/16/2018 02:44:04 AM