Into the mould
Fill tube
A few inches of tube carrying room-temperature water into a compartment well below freezing.
- What it does
- It is the delivery pipe between the inlet valve and the mould. Each fill runs down it at kitchen temperature and then stops, so whatever is left clinging to the inside sits in the coldest air the cabinet makes until the head calls for water again.
- Where it sits
- At the back of the freezer compartment: in through the rear wall, across the top of the ice maker and down over the fill cup. Which corner it enters by changes from one cabinet to the next, so it is found by following the tube rather than from a drawing.
- How it is tested
- By watching a fill, not by probing the tube. Sub-Zero is clear that nothing travels down here until the compartment has come to its setting and the head asks for water, so the cabinet is confirmed before the tube is blamed. A fill is then triggered and watched: a clean run, a dribble, or nothing at all.
- What the work costs
- Ice maker, water valve or supply line: $300–$820, after the flat $89 diagnosis.
Pattern
What we usually find
- The bin taken out for a party and the ice maker left switched on, so a cycle delivered a fill with nowhere to send it.
- Water shut off at the house valve while the machine was left running, which Sub-Zero lists among its own causes of a frozen fill tube.
- Supply pressure that rises and falls through the day, so some fills overshoot the cup and set around the mouth of the tube.
- A jammed cube holding the harvest part way, leaving the tube wet and the mould warm far longer than the cycle intends.
Most often first. Order comes from what the visits keep turning up, not from a count.
Two things make this the most-thawed part of a Sub-Zero. Warm water arrives in a compartment held around zero, and the tube is open at the bottom, so anything that leaves it wet at the wrong moment leaves it frozen a minute later.
Which is why a thawed tube proves nothing by itself. This is where the fault becomes visible; it is almost never where the fault begins.
Repair or replace
What usually happens to it
Usually cleared and proved rather than swapped. Ice inside the tube is a symptom of something above it, so the repair is the cause: a bin pulled out with the machine left running, water shut off while the arm stayed down, a jam, or supply pressure that wanders. The tube itself goes only when it is split, out of line or has been prised at.
Two follow-ups
Can I pour hot water down the fill tube to clear it?
No. Hot water sets again a little further along, it can soften the plastic, and it tells you nothing about why the tube iced up in the first place. Sub-Zero's owner-safe route is switching the freezer off for four to six hours. If it ices again, call Denver Sub-Zero Repair Experts.
Does a frozen fill tube mean the ice maker is finished?
Rarely. The head is usually intact and waiting for water it cannot get. What matters is which upstream fault filled the tube, because a defrost on its own buys a few days and then the same ice returns in the same place for the same reason.