A Sub Zero ice maker that freezes up may be the culprit of a fill tube frozen, a defective water inlet valve, low freezer temperature setting, or a water filter that requires replacement.
Prior to trying to work on the ice maker unit, see to it that all power and utilities have been shut down and unplugged. Initially, find the water line to the unit and switch off the water supply through the shut-off valve. You need to secure a bucket and cloth on hand for the excess water in the supply line.
The supply line and fill tube deliver water to the ice maker unit. The fill tube can have different components that connect to the water supply line, and it gets in the back of the fridge and in the ice maker. You may have to take off the ice maker to check the tube and check if it is iced.
When the fill tube is frozen, melt it out with warm water poured over the tube making use of a turkey baster, if not eliminate this part using the fridge and melt it out into the sink. You can take off the part at the back of your refrigerator by removing a few screws and disconnecting the water supply line. Melt it in the sink and reconnect.
Some of the alternative ways include using a hairdryer to melt out this part. Be cautious when utilizing the method as dropping water and power may result in possible electric shock. Moreover, exposure to extended periods of high temperature may damage the fill tube part.
Replace the water filter. When you have a fridge water filter, examine if it requires replacement, or think of changing it.
Reset the temperature. Look into the temperature setting as it may be adjusted too low. You would want to turn it up at least two degrees higher.
Try the water inlet valve. Test the water inlet valve. This part regulates the flow of water into the unit and is found in the rear of the fridge at the back access panel. In some cases, this component can go bad and overload the ice cube tray when it is not necessary.
The inlet valve comes with a screen filter that can be obstructed with debris and minerals from hard water. Uninstall the inlet valve from the fridge and utilize a flat head screwdriver to take off the sediment screen from the component. Clean the filter screen with warm water and soap and change it. Reinstall all parts and check the ice maker.