In the context of refrigerators, there is no such thing as a "sand timer". You likely mean the Mechanical Defrost Timer, which serves a similar countdown purpose but uses internal gears and a small motor rather than sand to measure time
The defrost timer is the "clock" that manages the automatic defrost cycle in frost-free refrigerators. [
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- How it Works: A small internal motor slowly turns a series of plastic gears. After a set period of cooling—usually 6 to 10 hours—the gears reach a point where they flip an internal switch.
- The Switch: The timer cuts power to the compressor and redirects it to the defrost heater.
- The Cycle: The "thawing" phase usually lasts between 20 and 30 minutes before the timer resets and restarts the cooling cycle.