Diagnosing Refrigerator Ice Maker Harvest Cycle Jamming Caused by Damaged Mold Coatings

Diagnosing Refrigerator Ice Maker Harvest Cycle Jamming Caused by Damaged Mold Coatings

A refrigerator ice maker that stops making cubes, quits in the middle of its cycle or leaves a frozen lump in the tray can throw a daily routine off course more than most people think. Many owners blame the water line or the temperature in the freezer and while both are common culprits, the culprit may be hiding inside the ice mold itself. Most ice makers have a smooth nonstick coated mold to aid the ice cubes release during the harvest cycle. When that covering is scratched, pitted or peeled, ice begins to grasp the surface and the ejector mechanism has to resist it. The result is a crowded harvest, a stressed motor and cubes that are uneven, hazy or missing completely. In this post, we will look at the harvest cycle, why mold coatings are important, how damage progresses, and how to reliably evaluate the problem before replacing parts you may not require.

How the Ice Maker Harvest Cycle Works

An ice maker just fills, freezes, harvests and resets. In the fill step, a water inlet valve injects a known amount of water in the mold cavities. The freezer then chills the water until a thermostat or sensor near the mold senses a temperature of about 15 degrees Fahrenheit, which tells it the cubes are solid. Then the harvest cycle begins and a little heater beneath the mold heats the surface just enough to release the outer covering of each cube. Then a motorized ejection arm turns, ejecting the cubes from their cavities and into the storage bin. When the arm returns to its home position, the cycle resets and the next fill begins. Resistance at harvest can break the chain of events

How Mold Coatings Help Release Clean Ice

Aluminum or a robust plastic is commonly used for the mold. Many designs incorporate a thin nonstick or anodized coating to the cavity surfaces. This layer minimizes the bond between the frozen water and the mold wall, so a little burst of heat is all it takes to liberate each cube. Without it the ice adheres tenaciously to the metal and the heater has to operate longer to remove the cubes. And a smooth finish helps the ice form with neat borders and uniform size. The ejector fingers are meant to push out cubes that are ready to leave—not to pry free cubes that are stuck. If the coating is intact, the harvest requires very little force, the motor operates softly and the gears last for many years. The whole system is pushed harder than its creators ever meant it to be when the covering is damaged.

How Mold Coatings Get Scratched, Worn or Peel

Physical deterioration is the most frequent cause of coatings failing. Coatings rarely fail without a reason. Using a knife, fork or screwdriver to chip away frozen ice can tear through the finish in one stroke, leaving bare metal exposed. Repeated heating and freezing cycles also stress the coating over time, especially on older systems that have a brittle finish. Hard water adds additional problem, the dissolved minerals leaving scale in the cavities that act like sandpaper on the surface. Harsh cleaners and abrasive scrub pads can destroy the polish, as can prolonged contact with chlorine or strong descaling solutions. Once a small patch of bare metal is exposed, moisture gets under the edges and rust lifts the coating around it.” It starts out as a light scratch and can develop into a rough, pitted area in a matter of months.

Why Damage to Coatings Causes Jamming during Harvest

The jam is caused by a change of ice release and that change is caused by a damaged covering. A cube freezing into a rough or bald region will stick far more firmly than it would on a smooth patch. Heater heats the mold. But the cube might be holding on still. Especially on one side. The ejector arm tries to raise a cube that’s still stuck on, and the motor pulls extra electricity as the arm slows or stops. In certain machines the arm just stalls until the control module times out and the cycle is incomplete. Partially released cubes can also become wedged between the fingers and the edge of the mold impeding the next rotation. “Continued pressure from the motor can actually peel the plastic gears inside the housing, and what started out as a minor coating problem becomes a broken assembly.”

Warning Signs of Damage to Coatings

Several indications indicate that the mold surface, not the water source, is the problem. If you hear a sluggish, strained grinding during harvest, followed by a stop and a second effort, it often signifies the cubes do not want to let go. Cubes that get fused together in bunches, or with jagged edges, may have stuck temporarily before breaking off. When the tray is empty, look attentively at the cavities, holding a flashlight to the surface to see whether there are any scratches, dull areas or small raised flakes. What’s very telling are the little black or gray flecks in the ice, or a faint peeling edge evident near the ejector route. If you see flakes of coating in the bin, dump that ice and do not use until the equipment is repaired or replaced.

Finding the Problem: Ruling Out Other Causes Before Pointing the Finger at Mold

The best approach is to eliminate the common ones first, as multiple different errors might cause a jam. Keep the freezer at a constant temperature of near-zero degrees Fahrenheit. A warmer compartment will yield soft, partially frozen cubes that stay together, no matter how good the coating is. Make sure the water supply has good pressure and flow, an overfilled mold makes huge cubes that span over cavities and obstruct the ejector. A bad thermostat or weak crop heater might also keep the mold too cold to release even on a perfectly flat surface. Check to see that the shutdown arm moves freely and that nothing in the bin is holding the arm in the elevated position. If all of these checks are passed and the cubes still stick to the mold then the coating is the prime culprit.

Step by step Inspection Diagnosis checks

First, disconnect the refrigerator or turn off the ice machine. Next, let the freezer warm up a little so you can safely handle the mold. Remove the bin and any ice that is stuck. Use lukewarm water to release it rather than a metal implement. In a good light, examine each hollow, running a fingertip over the surface and noting any rough or sticky spots. Compare the cavities with each other, because damage is usually localized to two or three places, not across the whole tray. Then restore power, start a manual harvest if your model has a test mode, and watch the ejector very intently. A pause in the same cavity in each cycle directly results in a damaged area. Take a picture of the surface so you have something to refer to. This can be helpful when you call a service or buy replacement parts.

Repair, Replace and Prevention Options

In most refrigerators the mold is integrated into a sealed ice maker unit, so refinishing seldom makes sense and replacement is the sure fix. An aftermarket solution exists in the form of nonstick sprays or food-safe silicone treatments, which can offer short-term respite for minor scuffs, but won’t heal significant scratches and may bring contamination risks. A new assembly usually bolts in with a couple of screws and a wiring connector and usually costs a lot less than a service call. Flush the water line and change the filter before installing to prevent silt from damaging the new surface. Never chisel ice off with harsh equipment to protect the replacement. Clean the mold carefully with mild soap. Keep the water filter fresh. In hard water areas regular descaling as well as a softener will increase the life of the coating.