I just replaced the diodes in the clock on my '83 300SD and tested it with 12vDC from a battery charger on the bench and it held excellent time for over five hours. Put it back in the car and... nothing. Tested power to it, getting 12v... WTH?

I'd be interested if anyone has any insight into this, too. I replaced the capacitor in the clock of my w124 and found the exact same thing - it worked fine when tested, only to once again barely keep time when back in the car.

I assume you meant 'capacitors' (plural)? Did you also use a power supply other than a battery when you tested it? Just curious.

Nope I meant capacitor, there is apparently only a single one in the clock of that era (1991). From memory I tested it using a battery, not a power supply.

Oh I see... I guess it's time to pull it back out and start over.

Don't forget, the ground is just as important as the +12 V.
Paul

__________________
84 500 SEL (307,xxx miles)

I saw that in another thread and I have an auxiliary ground wire going straight to the chassis.