Even after a full overhaul—including cleaning, polishing, and rebushing—vintage American movements like those from Ansonia and Sessions can sometimes suffer from abrupt, unexplained stops. When a movement runs perfectly on the bench for weeks but fails once cased or moved, the issue often points to subtle mechanical interference or environmental changes affecting the delicate balance of the gear train. Identifying why a clock stops suddenly requires a systematic check of the power delivery, the escapement geometry, and the external components that interface with the movement.
Quick Diagnostic Flow: Troubleshooting Abrupt Stops
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1. Does the clock stop at the same time every cycle?
- → Yes: Check for a bent tooth or debris on a specific wheel. The "abruptness" suggests a mechanical bind rather than a loss of power.
- → No: Proceed to Escapement & Beat Check.
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2. Is the "tick-tock" perfectly even?
- → No: The clock is "out of beat." Adjust the crutch until the cadence is symmetrical. An uneven beat is the #1 cause of sudden stopping.
- → Yes: Proceed to Component Interference Check.
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3. Does the pendulum wobble or touch the case?
- → Yes: Ensure the movement is seated level in the case. Even slight contact between the rod and the case or dial will stop the clock.
- → No: Movement may have an internal friction issue.
One common factor discussed in [repair forums](https://mb.nawcc.org/threads/clocks-abruptly-stop.198585/) is the behavior of lubricants over time. If a movement was properly serviced but used the wrong type of oil, or if it was over-lubricated, the pivots can develop a "suction" effect or attract microscopic debris that leads to intermittent stopping. It is essential to use high-quality synthetic horological lubricants that do not spread or gum up. Even a perfectly bushed movement will fail if the lubrication fails to maintain a consistent film between the pivot and the brass bushing.
The escape wheel is another high-sensitivity area for Ansonia and Sessions clocks. If the wheel is not perfectly true (flat), it may wobble as it rotates, causing the pallets to catch or "deep-lock" on only one side of the wheel's rotation. This often results in a clock that runs for several minutes or hours and then stops abruptly when the high point of the wheel meets the pallets. Inspect the tips of the teeth for wear or burrs, as even a tiny imperfection can interrupt the transfer of energy to the pendulum.
Finally, the pendulum rod and spring assembly must be checked for "twist" or kinks. A twisted suspension spring causes the pendulum to swing in an elliptical motion rather than a straight line, which creates friction in the crutch and leeches power from the movement. Furthermore, verify that the rod is not rubbing against the "lead-off" or any part of the case. In Sessions clocks specifically, the clearance between the pendulum and the back of the case is often minimal; if the clock is not tilted slightly forward or leveled correctly, the pendulum will eventually drag and cause an abrupt stop.
Why does my clock run on the table but stop in the case?
This is almost always a leveling or interference issue. The case may be slightly warped, causing the movement to sit at an angle that puts the clock "out of beat." Alternatively, the pendulum may be hitting the back of the case or the dial hole.
Can old mainsprings cause abrupt stopping?
Yes. If the mainsprings are "set" (lost their elasticity) or are coated in old, sticky grease, they may provide inconsistent torque. This can cause the movement to stop suddenly when the power demand is at its peak, such as during the start of a strike cycle.
How can I tell if my escape wheel is bent?
While the movement is running, observe the escape wheel from the side. If you see the teeth moving back and forth (weaving) relative to the pallets, the wheel or its arbor is bent and requires straightening to ensure consistent locking and drop.
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For projects requiring replacement movements, hands, pendulums, suspension springs, or other mechanical components, our detailed individual part photography eliminates the guesswork. Every piece in our inventory receives individual documentation showing its actual condition rather than generic stock photos, allowing you to buy with confidence.
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