Sub-Zero Ice Maker Making Hollow or Cloudy Cubes

Hollow cubes, undersized cubes and cloudy ice all get diagnosed as “the ice maker is dead” far more often than they should be. On a Sub-Zero the ice-making module seldom turns out to be the culprit. The water on its way to the mold is where we usually find the trouble.

What hollow cubes are telling you

A hollow or shell-like cube means the mold did not receive enough water during the fill cycle, froze what it had from the outside in, and harvested early. The harvest mechanism is working — you have cubes. The fill is short.

That points at everything upstream of the mold:

• a partially clogged water filter, by far the most common cause
• a failing water inlet valve that no longer opens fully
• a restricted or kinked supply line, often behind the unit after it has been pushed back into the cabinet
• low household water pressure, which on some Seattle homes with older plumbing is a genuine factor

None of those are the ice maker module. Swapping the module here is the costly wrong turn: a brand-new one starved of water turns out exactly the same thin, hollow shells as the old one did.

Cloudy versus hollow: different problems

It is worth separating the two symptoms, because they rarely share a cause.

Cloudy ice is an appearance problem. Dissolved minerals and trapped air make the cube opaque. It is a water quality issue and often improves with a fresh filter. Sub-Zero’s clear-ice systems freeze slowly and from one direction specifically to push air and minerals out, so when clarity degrades the water is usually the variable that changed.

Hollow ice is a volume problem, as above. A cube can be perfectly clear and still be hollow.

Small but solid cubes sit between the two and usually mean a mild restriction — enough to shorten the fill, not enough to hollow the cube.

What to try before booking a visit

Change the water filter, and note the date. This is the single highest-yield thing you can do, it costs very little, and filters are routinely left in far past their service life. Then give the unit a full 24 hours before judging the result — you are waiting on a complete production cycle, not a single harvest.

While you are there, check that the supply line behind the unit is not kinked. On built-ins that have been pulled out for cleaning or a previous repair, a crushed line at the back is not unusual.

If the cubes are still hollow after a fresh filter and a full day, the fault is downstream of the filter and it is a service call — most likely the inlet valve.

When it really is the module

There are symptoms that do point at the ice maker itself, and they look different from anything above: no harvest at all despite a full mold of ice, cubes fused into a solid block, the ejector arm stalled mid-sweep, or water dispensing into the bin instead of the mold.

Those are module and harvest-mechanism faults, and they are a genuine part replacement. The reason the distinction is worth caring about is cost — a valve and a module are not the same repair, and a shop that reaches for the module every time is charging you for the more expensive guess.

Questions that come up next

My bin never seems to fill. How do I know if that is slow?

There is no single figure, because output depends on the model and on how much ice the household takes. A bin that stays well short of full for several days, with good water pressure at the tap, points to a restriction in the supply rather than a failed module.

Will a fresh filter clear up cloudy ice?

It can. Cloudiness comes from air and dissolved minerals, and a new cartridge sometimes helps. Hollow cubes are a different matter: they come from too little water reaching the mold, and a filter change on its own will not put that right.

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