WORK | W111 VDO Kienzle Clock Repair

The dash clock stopped working in the Mercedes the other day and I've just managed to fix it. If you're in the same situation and expecting a large bill, as I was, don't worry they are very easy and inexpensive to fix.

There are number of good articles and pictures here and here. Plus if you have a copy of the Mercedes-Benz Technical Companion (Bentley Publishers (2005)) there is a very comprehensive article in there. I used a mixture of advice from different places and the following is what worked for me....

1. Remove clock from car

The clock is held in position by two sprung plates on either side of the clock body. Removing the clock from the car can, in theory, be done by depressing the springs by hand. I found this was impossible. It was much easier to get a screwdriver up under the dash and undo one of the cheese head screws holding the spring in place. The clock can then be easily lifted from the dash.

2. Dismantle clock

The plastic dust cap can be removed by unscrewing the three 5mm nuts on the rear of the clock. One of the nuts is protected by a plastic anti-tamper seal this will need to be broken away with a screwdriver. All the nuts are locked in place with thread lock, be careful I found this had gone hard and needed to be wire brushed away. The threaded stud may break if you use too much force. The dust cap will have a layer of black residue inside from the electrical points this should be cleaned away with a soft cloth.

3. Cleaning the mechanism

This was the most nerve racking bit of the process, I followed the instructions in the MB Technical Companion this involves washing the clock in a warm soapy water solution by suspending the clock in the water and jiggling it to clean it. After a couple of minutes in the cleaning solution I rinsed it in clean water and then gently dried the mechanism with a hair drier.

I came out looking clean and fresh!

Immediately after the clean I oiled the mechanism using a clock oil from R & N Horological. I got the T-S 289 Pen type oiler (refillable) for £3.50 which comes with it's own needle  and enough oil for a few lifetimes. Don't use WD40 or similar (as some suggest) this will clog up the clock and it will eventually stop it working. Oil all the bearings using small droplets of oil. Do not oil the jewelled balance wheel bearings.

I also gently filled the points with a points file to clean them up.

4. Repair

Once you look inside the clock you will probably find that the fuse has gone (good pics here). You're in luck if this is the case, it's an easy fix. The fuse is an electrical connection made with low temperature solder, when the temp rises it melts and springs open. I found some 100 degree solder (Tin/Lead/Bismuth mix) at C+L Finescale intended for model railways at £3.50 plus postage this did the trick nicely.

An alternative is to replace the fuse with a diode and capacitor as described in the MB Technical Companion, this suppresses the points. It is probably a good idea but I preferred having the original fuse in place just in case.

You may find, as in my case, that the points spring is broken I had to find a donor clock on ebay and take use the points from that one.

At this point you can hook up the clock to 12v and watch it working. It should look something like this... You can see the points touch and the winding mechanism fire at 40 seconds in.

Watch the points close at the 40 sec mark and the winder operate, I found it winds down and the points close every 2 minutes or so (apologies for "Just a Minute" in the background!) .

5. Reassemble

Ah the easy bit. Just screw down the dust cover using some loctite. In my case I also needed a need new bulb. This is 2w with a 9BA fitting, but be careful it has to have a small glass enclosure otherwise it won't fit (I've seen Thorn 37R, part no. 0022T4W quoted but I wasn't able to find this part). I found a couple at a local Autojumble.

6. Test

Testing involves hooking the clock up to 12v and letting it run for a few days. During this time you can use the small adjustment screw to get it running accurately (1/8 of a turn equals about 5min/day). I found it took a few days of playing to get in correct.

7. Return to car

Finally carefully push the clock back into position from the front of the dash and reattach the power plug. Now sit back a enjoy the sound of ticking!