Sub-Zero ice makers are built like the rest of the machine — conservatively and repairably — which is why most "ice maker died" calls we run end with a part around the ice maker, not the unit itself. The water's journey to the mold has several checkpoints, and ice quality tells you which one is failing before a single tool comes out.
Read the cubes like a technician
Small, hollow or crescent cubes mean the mold isn't filling fully — a flow problem: overdue filter, weak fill valve, low house pressure, or a partially frozen fill line. No cubes at all with the arm/sensor active means water never arrives or the maker isn't cycling — valve, frozen fill tube, or the unit's own drive. Cubes welded into a glacier in the bin means slow usage plus humidity, or a bin thermistor/airflow issue letting partial melt refreeze. Cloudy or off-taste ice is a filter and water-chemistry conversation, not a mechanical one.
The checkpoints, upstream to down
The filter (Sub-Zero's are honest about their 6–12 month life; overdue ones strangle flow), the fill valve (energizes on command; a meter and a flow test convict or acquit it in minutes), the fill tube (freezes into a plug when a valve weeps or airflow misbehaves), and finally the ice maker module itself — motor, thermostat, ejection. On units with in-door dispensing, the auger and chute door add two more suspects for "makes ice but won't deliver it."
The temperature detail everyone misses
Ice production is a thermometer in disguise. An ice maker only cycles when the mold reaches harvest temperature — so a freezer drifting from 0°F to 10–15°F (dusty condenser, tired gasket, door left ajar by a pickle jar) slows ice long before food complains. If your Sub-Zero's ice tapered off gradually rather than stopping cold, we check compartment performance first; the "broken" ice maker is often the canary for a cooling issue worth catching early.
Worth noting for local homes
Seattle-area water is soft, which is kind to valves and molds — scale is rarely our villain here. What we do see: remodel-era saddle valves and reverse-osmosis feeds that supply pressure at the bare minimum spec, where a filter at 80% life already tips production into decline. Part of a proper ice call is a pressure reading at the fridge, not just parts roulette.
The repair posture
Written quote once diagnosed, common valves and filters on hand, and the honest word when the module itself has earned replacement. On a Sub-Zero, it always pencils: these units have decades left, and ice is the cheapest system in them to keep perfect.