As moderator of the clock forum, I am seeing an increase in the number of people experiencing problems with pendulums not swinging (or not continuing to swing after being started). In most cases, this occurs after a clock has been moved from one location to another. Before a repairman is called, here are some initial things that can be done to possibly correct the issue.
Begin by making certain the movement (within the clock case) is perfectly level front to back and side to side. Once you have ensured that the movement is level, you may perform beat adjustment. Beat adjustment is the process of making certain the clock is in proper beat (characterized by an even “tick-tock” once complete). This process balances the verge, a see-saw like lever near the top of the movement, which controls the action of time train (escape gear). Note that newer movements may allow for automatic beat adjustment, but older movements may have to be adjusted manually. For auto beat adjustment, simply over-swing the pendulum (diameter of the pendulum bob + 6”-8”) to one side. Release the pendulum and allow the movement to self correct. If you do not know if your movement is equipped to self adjust, perform manual beat adjustment as described below.
Manual beat adjustment is a bit more involved, but is certainly not anything too complicated to do. Looking at the back side of the movement, the pendulum will hang from a piece called the pendulum leader. As you travel up the leader, you will notice an arm that sticks out through the rear movement plate. This arm, called the crutch arm, inserts through the pendulum leader just above the pendulum.
Remove the pendulum from the leader, and then remove the leader from the crutch arm. Take note of how these items are removed so that they can be replaced by reversing this process. Swing the crutch arm from vertical center to left, until you feel slight resistance. Return the crutch arm to vertical center and swing it to the right until you encounter slight resistance. For an even beat, the crutch arm MUST swing an equal distance from center to left, as it does from center to right. If the swing is shorter on one side, push through the slight resistance to adjust until the swing from center to left and center to right is equal. Re-mount the leader, re-hang the pendulum, and then start the swing. Note that further adjustments may be made if necessary.