OK, here's how they work. U-Line ice makers are controlled by a double-throw thermostat, that is the heart of the system. They call it a "cold control." The cold control has a screwdriver adjustment to control the temperature inside the "box" - it should always be set to the warmest possible position - don't ask why, just take my word for it. As long as the cubes remain good and hard, leave it at the warmest possible setting. If the cubes are soft and wet, then adjust it a little colder - no other time. When you first turn the machine on, the cold control is set in the cool down cycle. The compressor and fan run, cooling down the inside of the machine. On newer units, the cold control is located at the front of the machine, at the bottom, behind the lower grille; on older machines (before 1990), it was sometimes located at the rear of the machine. Anyway, it is a little box that has a capillary tube coming out of it and running up the rear of the machine, in through the rear panel, and into the inside of the machine. It fits into a hollow tube that runs into the actual mold. As the machine cools down, this capillary tube senses the temperature of the actual metal ice mold. When the temperature of the mold becomes cold enough that any water inside it will have frozen - whether there's water there or not - the thermostat switches positions inside (double-throw - it breaks the contact that runs the cool down cycle by turning off the compressor and fan and switches to its other internal position, initiating the "harvest cycle").
When the harvest cycle is initiated, the ejector fingers begin to rotate. As the rotation begins, a cam inside the actual ice making unit turns - this does a number of things. It turns on the mold heater, to loosen the cubes inside the mold. The fingers will come down on top of the ice and stall there, until the mold heater has heated the mold enough to loosen the cubes. Then the fingers will begin to move again, pushing the ice cubes out the rear of the mold area, and as it continues turning it will "flip" them forward into the ice bucket. The wire "bail arm" will rise upward. You will hear the cubes drop into the ice bucket. As the fingers continue turning, the wire "bail arm" will come back down, checking the level of the cubes in the ice bucket. If the level of the cubes in the ice bucket is high enough that the wire arm can't come all the way down, it will disable the ejection mechanism so that the ice bucket doesn't over-fill. You will hear the cubes (if there were any) dropping down into the ice bucket. Then, as it continues turning, the cam activates a switch that opens the water valve, bringing water into the mold for the next batch of cubes. Note: this is the ONLY way water will come into the ice mold. If all the earlier things haven't happened, water will NEVER come into the mold. You can hear the water running into the ice mold for several seconds, then it will stop. The incoming water will have warmed up the inside of the mold enough to re-set the thermostat, and it goes back into cool down mode. The fingers "park" and the compressor and fan come back on, and the machine begins to cool down again.
The most common problem with U-Line icemakers is that the thermostat fails over time, and it never goes into the harvest cycle. The machine gets cold but never delivers any cubes or takes in any water. Most people think that the water valve has gone bad. This condition is NOT due to a failed water valve; it is a failed thermostat (cold control). About 95% of the problems with U-Line icemakers can be corrected by replacing the thermostat. However, it is not an easy job, and it will require removing the machine from where it is installed. The thermostat replacement requires access to the rear area of the machine.
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