--- title: "Shallow or hollow ice machine cubes: the trough, scale and the thickness probe" description: "Lay a fresh sheet of cubes on a dark tray and read it. A lopsided sheet, a missing column and chalky edges each point to a different stage of the freeze." url: "https://icemachinerepair.center/guides/why-the-cubes-come-out-small-or-hollow/" date_modified: "2026-09-26" --- Common problems # Shallow or hollow ice machine cubes: the trough, scale and the thickness probe An ice machine making small or hollow cubes is usually short of water during the freeze or harvesting early: a low trough, a dirty inlet screen, a loaded filter, warm supply water, scale on the plate or a thickness probe out of adjustment. Owners can check the valve, the filter, leveling and cleaning; the probe and the cooling system belong to a technician. By [IceMachineRepair.center technical team](https://icemachinerepair.center/authors/technical-team/) Published September 26, 2026 ## At a glance. The shape of a cube is a record of the freeze that made it. A dimple, a missing corner or a sheet that is thick at the bottom and paper-thin at the top each points to a different stage of the cycle. Read the whole guide ### Normal bridge on a cuber About 1/8 inch Manitowoc's factory setting; Scotsman sets 3/16 inch on its modular cubers. ### Supply water the makers accept 40°F to 90°F on Manitowoc Hot water at the inlet gives shallow, incomplete cubes. ### Owner checks Valve, filter, level, cleaning date Each one is outside the cooling system. ### Technician territory Thickness probe, uneven fill, inlet valve Scotsman marks probe adjustment for the service tech only. In this guide 1. Reading a sheet of cubes before anything else 2. Water that runs short during the freeze 3. Scale on the plate and the distribution tube 4. The thickness probe and an early harvest 5. Questions ## Reading a sheet of cubes before anything else A modular or undercounter cuber freezes one grid of cubes joined by a thin web of ice called the bridge. When the sheet drops, it breaks along the bridge into separate cubes. Pull a handful out of the bin straight after a harvest, before they melt together, and lay them on a dark tray: the pattern is easier to read than any single cube. An ice machine making small or hollow cubes is telling you one of two things. Either the water stopped reaching the plate evenly while the ice was forming, or the machine decided to harvest before the ice was finished. The rest of this guide is about working out which, because the fixes do not overlap. - Every cube shallow and dimpled in the middle: water or timing across the whole plate. - Full cubes at the bottom of the sheet, thin or missing ones at the top: water not reaching the upper rows. - One column of cubes missing all the way down: a blocked hole in the water distribution tube. - Ragged, misshapen or chalky cubes: scale on the plate or in the water path. ### Nugget ice machines and dispensers Nugget and chewable ice does not come from a plate, so there are no cubes to go hollow. The equivalent complaint on a nugget ice machine is wet, slushy ice or small crumbly pieces, and it has its own causes in the auger and the water feed. The checks on water supply and scale below still apply to it. ## Water that runs short during the freeze During the freeze a pump lifts water from the trough to a distribution tube across the top of the evaporator, and the water runs down the plate and back into the trough. As ice builds, the trough level falls. If it started low, or if the pump is starving, the upper cells stop getting water before they are full and the machine harvests a lopsided sheet. Manitowoc's troubleshooting table lists the likely reasons: the water level in the trough too low, a dirty filter screen in the water inlet valve, poor water filtration, hot incoming water, a water inlet valve that is not working, pressure outside 20 to 80 psi, and a head sitting out of level. Most of those are visible from outside the cabinet. ### Warm water at the inlet Manitowoc wants ice-making water between 40°F and 90°F and says never to connect a hot supply. The usual way it happens by accident is a supply line teed off near a dishwasher or a water heater, or a long run of tubing through a hot mechanical room. Warm water freezes unevenly and costs both shape and output. ### A machine that is out of level A tilted head sends the water down one side of the plate. Both the head and the bin should sit level side to side and front to back, and a machine that was bumped by a cart or had a leg leveler shift on a wet floor can start making half-cubes on one edge. A small level on the top of the cabinet settles the question in seconds. Source: [Manitowoc — Indigo NXT ice machines, installation, operation and maintenance manual](https://dijf55il5e0d1.cloudfront.net/pdf/ManitowocIndigoNXTIceMachinesOperatingManual.pdf) — Shallow or incomplete cubes from probe adjustment, low trough, dirty inlet screen, poor filtration, hot water, inlet valve, pressure outside 20 to 80 psi, machine not level; ice-making water 40°F to 90°F; 1/8 inch bridge, one-third turn is about 1/16 inch; clean and sanitize at least every six months and discard ice made during cleaning; uneven fill means a service company checks the cooling system Close on a few thin, hollow cubes in the palm of a gloved hand beside an ice machine. ## Scale on the plate and the distribution tube Hard water leaves minerals behind every cycle, and they collect where the water is: on the evaporator, in the holes of the distribution tube, on the water level sensor and on the thickness probe. Scotsman's residential manual explains that purer water freezes first, which concentrates minerals in the reservoir water, and that the deposits eventually cause malformed cubes. It describes normal cubes on that machine as tapered cylinders and says ragged, misshapen ones mean scale must be removed. Scale on the probe has a second effect: it can make the control read the ice as thicker or thinner than it is. The cure in both cases is the cleaning procedure in the maker's manual, with the approved cleaner diluted exactly as printed. Every cube the machine makes while the cleaning cycle runs goes in the drain, not the bin, as Manitowoc instructs. - Check the date of the last cleaning against the manual: at least every six months on Manitowoc, a minimum of twice a year on Scotsman modular cubers. - Wear the gloves and eye protection the manual asks for, and stick to the cleaner and sanitizer it names. - Discard every batch made during the cleaning cycle. - If the machine needs cleaning much more often than the manual says, have the water tested. Source: [Manitowoc — Indigo NXT ice machines, installation, operation and maintenance manual](https://dijf55il5e0d1.cloudfront.net/pdf/ManitowocIndigoNXTIceMachinesOperatingManual.pdf) — Shallow or incomplete cubes from probe adjustment, low trough, dirty inlet screen, poor filtration, hot water, inlet valve, pressure outside 20 to 80 psi, machine not level; ice-making water 40°F to 90°F; 1/8 inch bridge, one-third turn is about 1/16 inch; clean and sanitize at least every six months and discard ice made during cleaning; uneven fill means a service company checks the cooling system; [Scotsman — C1448 and C1848 modular cuber installation and user's manual](https://www.scotsman-ice.com/service/User%20Manuals/17359902.pdf) — Bridge factory set at 3/16 inch; bridge thickness adjustment for the service tech only; too thin a bridge prevents proper harvest; clean and sanitize the water system a minimum of twice per year; [Scotsman Home Ice — SRC065 residential ice machine installation and user's manual](https://portal.scotsmanhomeice.com/ResourceCenter/Files/GetFile/SRC065_user.pdf/1271) — Purer water freezes first and concentrates minerals; normal cubes are tapered cylinders; ragged or misshapen cubes mean scale must be removed; softened very hard water can give white, mushy cubes ## The thickness probe and an early harvest On most cubers a small probe sits a fixed distance from the evaporator. When the growing ice reaches it and water bridges the gap, the control starts a harvest. If the probe is set too close, the sheet drops early and every cube is shallow; Manitowoc sets it to produce a bridge of about 1/8 inch and notes that one-third of a turn on the adjusting screw changes thickness by roughly 1/16 inch. That sensitivity is exactly why this is not an owner adjustment. Scotsman's modular manual labels bridge thickness as for the service tech only and warns that a bridge set too thin keeps the machine from harvesting properly. If the water and cleaning checks are done and the cubes are still shallow, book the adjustment. ### An uneven fill after cleaning When the trough is full, the distribution tube is clear and the sheet is still thin at the top, Manitowoc's table sends the next step to a service company to check the cooling system. That is a sealed-system diagnosis with gauges, and on a machine charged with flammable R-290 it is never something to probe from the outside. Source: [Manitowoc — Indigo NXT ice machines, installation, operation and maintenance manual](https://dijf55il5e0d1.cloudfront.net/pdf/ManitowocIndigoNXTIceMachinesOperatingManual.pdf) — Shallow or incomplete cubes from probe adjustment, low trough, dirty inlet screen, poor filtration, hot water, inlet valve, pressure outside 20 to 80 psi, machine not level; ice-making water 40°F to 90°F; 1/8 inch bridge, one-third turn is about 1/16 inch; clean and sanitize at least every six months and discard ice made during cleaning; uneven fill means a service company checks the cooling system; [Scotsman — C1448 and C1848 modular cuber installation and user's manual](https://www.scotsman-ice.com/service/User%20Manuals/17359902.pdf) — Bridge factory set at 3/16 inch; bridge thickness adjustment for the service tech only; too thin a bridge prevents proper harvest; clean and sanitize the water system a minimum of twice per year ## Where to stop Stop and book if the cubes stay shallow after cleaning with the maker's products, if the sheet is thin at the top with a full trough, if the trough goes on filling after the machine is switched off, or if you would have to adjust the thickness probe to go further. Panels stay closed while there is power to them, refrigerant lines are never opened or pierced, and descaler is mixed only at the strength printed in the manual. Written by [IceMachineRepair.center technical team](https://icemachinerepair.center/authors/technical-team/). Our ice machine technicians write these guides from their own service calls and each maker's published manuals. Sources: [Manitowoc — Indigo NXT ice machines, installation, operation and maintenance manual](https://dijf55il5e0d1.cloudfront.net/pdf/ManitowocIndigoNXTIceMachinesOperatingManual.pdf) · [Scotsman — C1448 and C1848 modular cuber installation and user's manual](https://www.scotsman-ice.com/service/User%20Manuals/17359902.pdf) · [Scotsman Home Ice — SRC065 residential ice machine installation and user's manual](https://portal.scotsmanhomeice.com/ResourceCenter/Files/GetFile/SRC065_user.pdf/1271) For the heart of your home. ## Questions owners ask. ### Are small or hollow cubes safe to use? A shallow cube is no less safe than a full one. Ice that is ragged and chalky from scale, or that smells, says the water path needs cleaning, and the machine should be cleaned and sanitized before the next service. ### Can a water softener cause soft or odd cubes? Scotsman notes that softened water may not help an ice machine and, where water is very hard, can give white, mushy cubes that stick together. A water specialist can recommend a treatment made for ice machines. ### Why are the cubes fine in the morning and small by afternoon? Warmer supply water and a hotter room in the afternoon both change how the plate freezes. If the change is large, check the supply line route and the air around the machine. ### Should I turn the thickness probe myself? No. A small turn makes a large difference, and too thin a bridge stops the machine harvesting properly. It is a quick adjustment on a visit. ## The problems behind it. Each has a page of its own: what it usually means and the causes in the order worth checking. [All 17 problems](https://icemachinerepair.center/problems/) Problem ### Ice Machine Cubes Coming Out Thin, Small or Hollow 6 causes, cheapest first Problem ### Cloudy, Soft or Wet Ice From an Ice Machine 6 causes, cheapest first Problem ### Ice Machine Not Harvesting: Ice Stays Stuck on the Plate 6 causes, cheapest first Problem ### Ice Machine Making Too Little Ice for the Rush 6 causes, cheapest first ## When it needs a technician. The repairs on the right are where this guide ends when the checks do not settle it. ### Ice machine water valve and filter repair The inlet valve, filter, sump float or level probe and supply line, tested and replaced when water arrives short, dirty or nonstop. ### Ice machine harvest repair The hot gas valve, harvest assist, curtain switch and thickness probe that decide when a sheet of cubes is done and make it drop. ### Ice machine cleaning and sanitizing Scale off the evaporator and distribution tube, slime out of the bin, curtain and drain, with the maker's cleaner and sanitizer on its schedule. ### Ice machine compressor and sealed system repair The compressor, its start parts and the sealed system, including machines on flammable R-290, tested for pressure and leaks and repaired by the maker's procedure. ## More in common problems. What an ice machine means when the bin stays low, the cubes come out thin, hollow or cloudy, the ice tastes of something it should not, or a light keeps asking for a cleaning you already did. [The whole section](https://icemachinerepair.center/guides/common-problems/) What the ice is telling you ### Why an ice machine makes less ice: room heat, a clogged condenser and a slow fill Output slides a few pounds a day before anyone notices. How cycle time, clearance, the air filter and supply pressure decide the daily total, and which stops mean a technician. What the ice is telling you ### Ice machine ice that tastes musty, chemical or of the room: from the tap to the bin Taste the tap water beside a melted cube first. Then the filter, biofilm on the curtain, the scoop, the drain and whatever sits near the air intake. Guides ### All 18 guides Six sections, by what you are trying to find out. --- **[Read on the site: Shallow or hollow ice machine cubes: the trough, scale and the thickness probe](https://icemachinerepair.center/guides/why-the-cubes-come-out-small-or-hollow/)** **[Book a visit with IceMachineRepair.center](https://icemachinerepair.center/schedule/)**