The reasons why an ice maker may produce too much ice vary based on the type of ice maker. Common causes include an issue with the shut off arm or a defective control module.
The shut off arm, also known as the feeler arm, goes across the top of the ice bin. When ice reaches the top of the bin, it pushes the arm up, which halts the ice production. A damaged or broken shut off arm needs to be replaced, because it won't stop the ice production. Certain refrigerators have a freezer shelf that raises the ice bin. An incorrectly-installed shelf renders the shut off arm incapable of judging the bin's ice level, which causes an overproduction of ice.
If the shut off arm doesn't appear damaged, it can be tested by turning the freezer off, lifting the arm to its top position and turning on the freezer again. Any ice production indicates a defective control module which needs to be replaced.
Ice makers are either modular or component-based. Modular ice makers have groups of components formed together. Component-based ice makers tend to be more advanced and are made up entirely of individual components, allowing each one to be replaced if necessary. Component ice makers should be taken apart if they produce too much ice. Each component can then be checked for damage.