Perhaps it was me! The clock is likely an "electro-wind" clock. Meaning, it has a spring to provide energy to run the clock and a solenoid to tension the spring (effectively winds it up). There is a set of points on the mechanism that closes as the spring loses tension. The points close and momentarily connect 12 volts to the solenoid. The solenoid engages, pulls tension up on the spring and also opens the points once more. This cycle occurs about every 30 seconds.
To test the clock, remove it from the car to your work bench. You'll need a source of 12 volts to test it. Connect 12 volts (+) to the clock lead and 12 volts (-) to the case of the clock. Look at the mechanism and find the solenoid and spring mechanism. When you attached 12 volts, did the clock make a sound like "ZZZick?" That sound was the sound of the clock winding itself. If it did not make this sound, then the clock is already wound but not running or the points or solenoid are bad. If the points are visibly closed but the clock didn't wind, then remove the 12 volts temporarily and burnish the points with a metal fingernail file or swiss file. Try again. If it was only the points the clock may wind up when you reapply 12 volts. If this doesn't do it, then perhaps the solenoid is bad. To check this, you'll need to get more inventive. Remove the 12 volt (+) wire and attach it to something you can probe with (test lead with pointed tip or nail or small screwdriver). Probe the solenoid wiring (points to solenoid) and see if you can get the solenoid to engage. If you can't you better start looking for another clock. There are places that rework these, so don't muck it up.
Okay what if the solenoid works and the spring tensions but the clock doesn't run. How good are you with small stuff? One wound up theres a balance spring and wheel. It has a tiny circular spring. Be very careful not to damage the spring while rotating the balance wheel either way. Once the hairspring is tensioned, it will run the balance wheel. If it runs but quickly stops, the clock axles probably havent been lubricated in a ***** age. Using a toothpick lubricate all the axle shafts you can see with tiny amounts of very light machine oil (3-1 oil is about the heaviest you can use, preferably use sewing machine oil). Put a tiny droplet on each axle and on any pivot points you see. Try moving the balance wheel once more. If you get the clock to run, it will start lubricating its parts by spreading the oil.
If you can't get it to run, then take it to a clock maker or send it off to a repair shop.
Hey geegee thanks for the clock info. /forums/images/icons/cool.gif I might get brave and take a look at my clock's guts now that I know what I'm looking for. One other thing, a long time ago there was a little repair shop that I could take my tach and clocks to. But he has long since moved or retired. /forums/images/icons/frown.gif But the one thing I remember him saying about Ford clocks was that if the car battery is dying (low voltage) that was very hard on the clock's solenoid. fd