Refrigerator Ice Maker Making Hollow Ice Cubes — 3 Common Fixes

You poured the lemonade for the kids’ birthday party, dropped in some ice from the door dispenser, and immediately noticed the cubes looked wrong. Each one was crescent-shaped but hollow in the middle, like ice shells. They melted in 90 seconds. The lemonade was warm by the time the cake came out. You glanced at the Whirlpool side-by-side and wondered when, exactly, the ice maker started cheating you.

Hollow or partial ice cubes are one of those problems that nobody calls a tech about for months, because the ice maker is still technically making ice. It’s just bad ice. The cubes look wrong, taste wrong, and melt fast. In Miami where ice goes into pretty much everything from coffee to cocktails to coolers, bad ice gets old quick. Here are the three causes that account for about 90% of hollow-cube complaints, and the fixes for each.

How a Normal Ice Maker Should Work

Before troubleshooting, a quick refresher on what the ice maker actually does. The standard automatic ice maker (made by Whirlpool, Frigidaire, GE, or a sub-supplier under license) works like this:

1. Water inlet valve opens, fills the ice mold with about 3 ounces of water
2. Mold sits at freezer temperature for 35-50 minutes until water freezes solid
3. A thermostat in the mold detects the frozen state
4. Heater under the mold warms the cubes slightly, releasing them from the mold
5. An ejector arm sweeps the cubes out into the storage bin
6. Cycle repeats

A normal cube is fully solid, slightly cloudy in the center (dissolved air), and weighs about 6-8 grams. A typical fridge ice maker produces 3-4 lbs per day.

A hollow cube means one of two things: not enough water entered the mold, or the cube was ejected before it finished freezing solid. Both have specific causes.

Cause One: Low Water Inlet Pressure

The most common cause of hollow cubes is insufficient water entering the mold during the fill cycle. The fill cycle is timed (most ice makers fill for 7-12 seconds at a specific flow rate). If pressure is low, less water enters in the allotted time, and the resulting cube is undersized.

Refrigerator ice makers require a minimum of 20 PSI of water pressure at the inlet valve to fill correctly. Most municipal water systems in Miami-Dade and Broward run 50-70 PSI at the meter. But by the time water gets to the ice maker, several things can drop pressure:

Plumbing run length: Long water lines from the meter to the fridge (200+ feet through a slab) lose pressure.

Saddle valve restriction: Older installations used saddle valves (the small clamp-on valves with a piercing screw) on the cold water line. These reduce flow significantly even when fully open. If you see one in your install, replace it with a proper tee fitting and shutoff valve.

Inline filter clogged: Most newer fridges have an inline filter (Whirlpool W10295370A, Samsung DA29-00020B, GE XWFE, etc.) that filters water for both the dispenser and the ice maker. After 6-12 months these filters clog and significantly reduce flow. Replace per manufacturer schedule, in South Florida (high mineral content water) usually every 6 months.

Frozen water line in the freezer wall: Less common but happens. A small ice plug forms in the water line where it routes through the freezer ceiling. Symptoms: hollow cubes that gradually get smaller over weeks, eventually no cubes at all.

The fix for pressure problems: replace the inline filter, check the saddle valve, verify the shutoff valve under the sink is fully open. If you’re handy, you can also measure flow at the back of the fridge by disconnecting the line at the inlet valve and timing how long it takes to fill a 1-cup measure (should be under 30 seconds for adequate flow).

Cause Two: Failing Water Inlet Valve

The water inlet valve (Whirlpool WPW10300024, Samsung DA62-04102B, GE WR57X10032, depending on brand) is a small electromagnetic valve at the back of the fridge. When the control board signals “fill,” the valve opens for the timed fill cycle and water flows. After thousands of cycles the diaphragm inside hardens and doesn’t fully open, restricting flow.

You can test this with a multimeter on resistance (ohms). A good ice maker inlet valve solenoid reads 200-500 ohms. Open coil reads OL. If electrical resistance is good but the valve isn’t filling properly, the diaphragm is mechanically failing.

Replacement runs $40-90 depending on brand. The labor is straightforward: shut off water at the supply, unplug the fridge, remove the back panel, swap the valve. About 30-45 minutes for a comfortable DIY-er.

Don’t ignore a failing inlet valve. The same valve sometimes fails in the opposite direction (stuck partially open), which causes the inlet to drip continuously and the freezer to slowly flood. We’ve seen this cause damage to the wood floor in front of fridges in Aventura and Sunny Isles units, sometimes thousands in subfloor repair.

Cause Three: Ejector Cycle Timing Off

If the ice maker cycle ejects cubes before they’re fully frozen, the cubes come out semi-solid. The center is still liquid water at that point, and that liquid drains out when the cube hits the bin, leaving a hollow shell.

The ejection trigger is controlled by a small bimetal thermostat (or thermistor on newer models) attached to the mold. When the mold reaches approximately 15 F, the thermostat closes and triggers the ejection cycle. If this thermostat fails or has drifted, ejection happens too early at warmer mold temperatures.

The other thing that can cause early ejection: freezer ambient temperature too warm. The ice maker assumes the freezer is at 0 to -5 F. If the freezer is running at 10-15 F (because of a door that’s not sealing, a failing defrost system, or thermostat drift), the bimetal still cycles but the cubes don’t have time to freeze through.

Check freezer temp with a separate thermometer. Place a glass of water in the freezer overnight, in the morning it should be solid through and the temperature should read at or below 5 F. If it’s warmer, fix the freezer temp problem first, the ice maker will resolve once temps are right.

If the freezer is at proper temp and you’re still getting hollow cubes, the ice maker module (which contains the bimetal thermostat) needs replacement. Whirlpool module assemblies are $40-100. The whole modular icemaker is sometimes easier to replace than just the thermostat.

Other Causes Worth Mentioning

Mineral deposits in the mold: Miami water is hard. Calcium and magnesium deposits build up on the mold surface over years and act as insulation, slowing the freeze. Symptoms include hollow cubes and cubes that stick in the mold (the heater can’t release them). Run a vinegar cleaning cycle if your ice maker has one, or remove the ice maker and soak the mold in white vinegar for an hour.

Recently after replacing filter: When you replace the water filter, the first 2-3 batches of ice will be smaller and may have hollow centers. The filter housing has air in it that needs to flush through. Discard the first batches and the cubes should normalize.

Recent power event: After a power outage or significant brownout (very common in summer storm season here), the ice maker can be temporarily out of calibration. Wait 24-48 hours of normal operation before deciding something is wrong.

When to Call a Tech

If you’ve checked the water filter, the freezer temperature, and the water pressure and you’re still getting hollow cubes, the inlet valve or ice maker module needs replacement. Some homeowners do this themselves, others prefer a tech.

Berne Appliance Repair carries common inlet valves and ice maker modules on the trucks. Most ice maker calls finish in one visit. $59 service call, waived on repair. We service Whirlpool, KitchenAid, Maytag, Samsung, LG, GE, Frigidaire, and Sub-Zero.

Call (754) 345-4515 or book through our refrigerator repair page. For specific service areas see ice machine repair in Boca Raton, refrigerator repair in Coral Gables, or appliance repair in Bal Harbour.

Hollow cubes are usually a 30-minute fix once you find the cause. Worth fixing because bad ice ruins drinks and a properly tuned ice maker should last 8-10 years before the next service.