If a check of the electrical connections doesn't show any problems then most likely the problem is internal to the clock. You don't mention whether ot not the clock is the "big one" or the "little one". Although the clocks have very similar movements the small one is rather difficult to disassemble without damaging it. If it is the large clock you could remove it and try cleaning the works with a solvent like electronic contact cleaner but it would be much easier to hit the wrecking yards or e-Bay...

Good luck,

Justin B.