W126 Clock Help Needed

[rdaufan]

After reading some prior posts about clock repair in the W126, I replaced the capacitors for the clock in my '86 560SEL. I tested before I installed on a 12 V battery and it ran fine for 15 minutes before I put back in cluster and installed. Now, the clock will only run for about 5 minutes and then stop. I have attached a 12 volt battery directly to the clock and still only running for about 5 and then stopping. This is the second clock I have installed and both have the same symptoms. I replaced the capacitors on both. Does this sound like a ground or power issue? Or possibly some bad capacitors? I bought the 2 pairs of capacitors from Radio Shack at different times, so would be odd for it to be capacitors. Is the power lead to clock suppose to be on constant power...12V? Any help would be appreciated.