A pendulum clock in need of repair does not require a trip to the clockmaker and an expensive repair bill. A clock running too fast or too slow, a clock that stops running or runs intermittently, does not chime or chimes out sequence are all repairs you can make at home. With a gentle hand and a little patience, you can put your pendulum clock back in good working order.
Adjusting the pendulum
Ensure clock is on a level surface. Both mantle and wall clocks must rest on a level surface to keep correct time. If necessary, place a shim no larger than 6mm (1/4 inch) underneath a mantle clock to level it out. Verify the level is correct with a straightedge level. To level a wall-mounted clock, move the bottom of the clock casing to the left or right, no more than 1.5 mm (1/16 inch).
Adjust the pendulum up or down. A pendulum too high causes the clock to run fast; too low causes the clock to run slow. Locate the adjustable weight, or screw mechanism, near the pendulum arm. Shorten the pendulum by turning the screw mechanism to the right, 1/2 turn. Lengthen the pendulum by turning the screw mechanism to the left, 1/2 turn. Restart the clock and check it against your computer clock or watch. If it is obviously running too fast or slow, repeat the process. Otherwise, wait to two or three days and recheck it.
Set the clock in beat. A pendulum clock in correct beat should have a steady, rhythmic tick-tock, tick-tock sound. An out-of-beat clock will not keep correct time and may stop working altogether. To set the clock in beat, reposition the crutch of the pendulum. The pendulum crutch is a small piece of wire that goes through the pendulum arm. The centre motion of the crutch must be in the centre of the clock. Using a gentle hand, bend the crutch in the middle of its length to the desired position. Swing the pendulum and listen for a steady, tick-tock sound.
Checking the beat
Make sure the clock is on a level surface and fully wound.
Check the clock hands and pendulum arm to make sure they are not bent or touching each other. If they are, gently bend them back into the correct position.
Adjust or reset the clock beat.
Time and chimes
Make sure chimes are not set to "silent."
Adjust the minute and hour hands. Using a pair of pliers, remove the nut holding down the minute hand and rotate it through the chimes until it chimes at the top of the hour. Count the strikes and reinstall the nut. Slip the hour hand around to the hour that just struck.
Adjust the clock weights. A tall pendulum clock, such as a grandfather clock, must have the weights working in correct order for chimes to ring. The weight on the right controls chimes, the weight in the centre regulates the pendulum and the weight on the left regulates the hour strike.
Do not expect a pendulum clock to keep perfect time. A deviance of at least one to two minutes per week is normal.
Handle a pendulum clock with care. Internal clock mechanisms are delicate and can easily bend or break.