Almost every ice call arrives described as a failed ice maker. The module itself is one of the least likely causes, and separating the real ones takes about fifteen minutes in a fixed order.
Read the freezer first
An ice maker needs the freezer compartment at or below 5°F to produce. Sub-Zero recommends 0°F. A compartment sitting at 7°F or 8°F will keep food frozen indefinitely and will simply stop harvesting, and the homeowner will book an ice maker repair for what is a refrigeration fault.
So the first measurement on every ice call is the compartment, not the module. If the freezer is above the production floor, the ice maker is behaving correctly and the real question is why the compartment drifted. On a full-size cabinet with two sealed systems, that is a fault on the freezer circuit specifically. On a column it is the only circuit there is. Either way, replacing the ice maker would have fixed nothing.
Then measure the fill
With the compartment at setpoint, the next question is how much water is arriving, and it is a measurement rather than a judgement. A fill that is thirty per cent short still looks like water going in.
Thin, hollow or undersized cubes are the signature of a short fill, and the cause is upstream of the mold. In the order they are worth checking: a saturated filter restricting flow, a supply shutoff or saddle valve never fully reopened after earlier work, a kinked or crimped supply line behind the cabinet, low inlet pressure, and finally the water inlet valve itself failing to open fully.
Only the last of those is a part. The rest are found by looking, and they are the reason we do not order a valve from a phone description.
Then read the harvest
If the fill is correct and the cubes are full size but will not come out, the fault is in the harvest cycle rather than the supply.
A stalled ejector, a mold thermostat that never satisfies and a mold heater that has failed open all present the same way from the front: a full mold that stays full. They are distinguished electrically, not visually, and this is the point at which the panel comes off.
The fill tube is a separate fault with its own unmistakable signature. Water arrives, misses the mold, freezes at the back of the compartment and builds the slab that people report as the ice maker overflowing. The tube has been diverted or its heater has failed. Nothing is wrong with the mold.
Filters, by series
A water filter is a taste and sediment filter and it is a maintenance item rather than a repair part. The reason to change it on schedule is flow: a saturated filter restricts the supply and produces exactly the thin-cube symptom that a failing inlet valve produces, which is why the fill is measured rather than assumed.
The twist-in filters are 4204490 and 9030868, fitted to Classic and legacy Built-In cabinets, Designer and legacy Integrated cabinets, the 648PRO, the PRO3650 and the PRO4850. The push-in filter is 7045454, which replaced 7023812; the older 7005017 and 7023811 are discontinued. The UC-15I undercounter ice maker takes 7042803, which replaced 7012333. The air purification cartridge is a separate item, 7042798, and it does nothing for water.
The machine’s own environment
Undercounter ice makers deserve their own paragraph, because they fail for a reason the built-in ones do not. They breathe through a single low grille that does both intake and discharge, and they run a small mold hard. Block that grille with a cabinetry change, a toe-kick panel or stored boxes and production falls off long before the cabinet itself warms enough for anyone to notice.
Outdoor installations under a lanai are the extreme version. An indoor-rated machine working against ambient air in the nineties runs continuously, drifts through the afternoon and recovers overnight, and no part replacement changes that. We measure air temperature at the grille before quoting, because sometimes the honest answer is placement.
What actually gets replaced
Fill valves, fill tubes and tube heaters, ejector assemblies and mold thermostats account for most of the parts on this repair. The module as a whole is replaced far less often than it is blamed.
Serial numbers matter more here than people expect. Ice maker assemblies changed across the production runs of the same nominal series, so the plate decides which part fits and we read it on site rather than ordering from a model number quoted over the phone. Where a component is on backorder we say so before the visit rather than after the cabinet is open, because a week’s lead time belongs in your decision rather than in a surprise.
Cost and coverage
$80 flat diagnostic, credited toward the repair. Written estimate before any part is ordered. Genuine OEM parts, 90 days on labor, 365 days on parts. If the display is showing a service code, leave it in place for the visit.