Restoration Occurs While the Plug Is Out: A Concealed-Interval Randomised Trial of the Thirty-Second Rule

The instruction is always the same — unplug it, wait thirty seconds, plug it back in — and nobody has ever explained the thirty. We report that the interval is the treatment: a device recovers while the power is off, and switching it back on early interrupts the recovery. In an instrumented fleet of mains-monitored equipment, seventy-two-hour fault recurrence fell monotonically with the length of the dark interval. Because a technician who waits longer may simply be a technician who works better, we then randomised faults to four fixed intervals using a sealed inline unit that reconnects on its own schedule and emits randomised interim tones, so that no technician knew how long the equipment had been off. Recurrence was $34.1\%$ after half a second and $8.8\%$ after two minutes. Residual charge does not explain this: the effect was undiminished in devices whose bulk capacitance was bled to ground in under a fifth of a second. Restoration follows a saturating exponential with a half-time of $19.4\mathrm{s}$ (95% CI 17.8–21.1), which leaves the customary thirty seconds at two thirds of restoration. We propose no mechanism. We propose a minimum of ninety seconds.Switching it back on does not repair the machine; it only ends the repair.