it sounds like you are describing the ice thickness probe, it should not actually be touching the grid though; you should have a 3/16" gap for the correct bridge. If that is what you are talking about, it does not shut off or keep the unit running, it only senses when the ice is large enough to harvest, the magnetic curtain switch will terminate harvest after ice has fallen or turn the machine off when the ice fills the bin enough to keep the curtain open.
The ice thickness probe after the cold water that runs over the ice touches for 9-10 continuous seconds initiates the harvest cycle. Please note that for the first 5 minutes of the freeze cycle the control board won't allow the unit to harvest
You didn't state the make of the machine, but many of the ice plate covers will not return to closed position and go back into freeze if the machine is not level. The cover has a magnet that activates a reed switch to tell the machine harvest is complete and the bin is not full so it can start to freeze again. If the cover is warped, bent, or has a cracked pivot at the top it will not function as intended.
Also the ice probe has to be clean and not conduct current due to mineral build-up or un rinsed cleaner. Cleaner is Phosphoric acid and conductive if not rinsed properly and dried. It will cause the machine to go into error due to long freeze cycle.
I have also seen a dirty spray wand cause water to go onto the harvest sensor and cause a early harvest.
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