Removing, Disassembling and Repairing the Dash Clock

Kevin Sweeney (CSR Newsletter XVI 1/2)

(Editor's Note: Back in Volume XV, we got you started on fixing your mechanical clock by revealing the secret of removing it from the dash and then we stopped. In consideration of the fact that many of you have been left so long with said instrument dangling from the dash by its wires and yet refrained from issuing death threats, and that we have had a number of new members, herewith follows the complete procedure.)

This is a process for removing, disassembling and actually repairing the mechanical VDO clocks found on the older coupes. The repair requires no special tools and no special technical or mechanical abilities.

Removing the Clock from the Dash

Remove the under dash , driver's side vinyl (cardboard) trim panels. (Keep track of which screws go where. Some are different originally and some have been replaced with something else by a PO. Editor) Reach up under the dash and feel around for the two long (about 3 in) plastic nuts that hold the clock in place. The nuts are shaped like cigarettes. Remember that since they are facing you, you turn them what seems like clockwise to loosen. When they are loosened, a very slight rotation of the clock will free it up. If you can't get the clock free by loosening the nuts, remove them completely. It's a little tight under there, but some patient fiddling will get the clock past the metal dash supports. If you have very large hands and arms, you may want someone else do this for you. There is a flimsy paper gasket between the back of the instrument panel and the clock, so be careful not to damage it when you pull the clock. Pull (gently) the wires off the back of the clock, and label them or make a note of what they do. On mine red was 12v, brown was ground and another was for the clock's illumination.

Disassembly

The metal back comes off the clock. There are three small nuts that hold it in place. Two are obvious, the third is covered with a green warranty protecting seal. Scrape the green stuff out and loosen that nut. The back can now be removed. Mine took a good deal of cajoling, but it will come off. Friction and about thirty years are the only thing holding it in place.

Clock Theory

This is the fun part. The clock is not an electric clock at all, it is mechanical. The twelve volt connection powers a tiny solenoid which winds the clock once a minute. Those of you that have a functioning older clock can hear this operation if you sit quietly in your coupe with the engine turned off. Once a minute you will hear a soft "plunnnggg" (sic. Editor) sound coming from the direction of the clock. That ís the sound of the solenoid winding the clock's mainspring. The solenoid is actuated by a pair of contacts, (they look just like points) which come slowly together as the clock ticks. After closing, the solenoid is activated, which winds the mainspring, which, through a system of gears, opens the points. This process repeats itself once a minute. The mainspring is a low tension gizmo, unlike the ones found in a conventional mechanical watch or clock, because it only has to keep the clock running for a little over a minute.

Clock Fix (continued)

What's wrong with your clock?

The problem with most of these old clocks is simple and easy to fix. The contacts that close to activate the winding solenoid become fouled, and the clock stops winding itself. Usually all that is needed to get your clock running is to clean the points. I used 200 grit sandpaper, but you may want to go to an electronics shop a buy some contact cleaner. If your clock is stopped with the contacts in the closed position, this is almost assuredly your problem. Clean the contacts, apply twelve volts DC to the clock and see if it springs to life. If you can see and hear the solenoid operating, your clock is probably fixed.

You may run into another problem after getting the solenoid operational. After not running for years, the clock mechanism may be a little stiff, and may not want to keep ticking for a full minute. What you need to do is help it along either by shaking the clock or by VERY GENTLY giving the WHEEL?? a little nudge when it stops. If you keep doing this, your clock should loosen up to the point where it will run for a whole minute. When that happens, your clock is fixed. You should keep it hooked up to the twelve volt source for a few days to make sure it's running right, and to see if it gains or looses time. There is a tiny adjustment screw on the back of the clock if it runs slow or fast.

I ran into a slightly different problem with another clock. The tiny printed circuit board associated with the solenoid had a problem. The printed circuit that carried the twelve volts to the solenoid had lifted up off the board and no longer contacted the twelve volt wire. I simply soldered the twelve volt wire straight to the separated printed circuit.

After your clock has been running fine for a few days or more, it's time to reinstall it. Push the plastic back into place and replace the tiny nuts. Reconnect the wires and secure the clock in the dash with the plastic nuts, remembering to replace the flimsy paper gasket.

I have resurrected two clocks in this fashion and both are ticking along flawlessly for over a year now.

(Editor's Note: As a scientist, I observed a direct correlation between the mean ambient temperature in my garage and the rate at which my clock - which has never been removed - lost time. This thus makes it possible to track prevailing atmospheric conditions by proper calibration and careful (i.e.: anal retentive) record keeping. Conversely, those who really need therapy, can keep records of temperature and thus properly adjust the clock to an accurate representation of GMT.)