--- title: "Freezers" description: "Sub-Zero freezers — column freezers and freezer sections that frost over, run warm, or never quite hold their set point." url: "https://subzeromiami.support/appliances/freezer/" date_modified: "2026-08-18" Appliance type: "Freezers" --- # Sub-Zero freezers ### Frost is a symptom, not a diagnosis Heavy frost inside a column freezer almost never means the freezer is running too cold. It usually means warm air is getting in or the defrost cycle is not finishing: a tired door gasket, a defrost heater that has failed, a thermistor reading wrong, or a drain that has iced over. Each is a different repair at a different figure, which is why the diagnosis comes before the quote. ### What we check first - The door seal and how the door sits — the cheapest cause, and the one most often missed - The defrost heater and thermistor, tested rather than assumed - The evaporator and the drain line - Stored codes, which say what the unit has been doing rather than what it is doing now ### After a power cut Storm season brings its own version of this: a freezer that came back up but never quite recovered, or one that restarted with the ice maker out of step. Worth checking the same week rather than the same season — a unit that is running but struggling is quieter about it than one that stopped. Column & over-and-under Freezer repair Heavy frost build-up Defrost heater and thermistor failures Door and gasket sealing Frost is a symptom, not a diagnosis Heavy frost inside a column freezer almost never means the freezer is running too cold. It usually means warm air is getting in or the defrost cycle is not finishing: a tired door gasket, a defrost heater that has failed, a thermistor reading wrong, or a drain that has iced over. Each is a different repair at a different figure, which is why the diagnosis comes before the quote. What we check first The door seal and how the door sits — the cheapest cause, and the one most often missed The defrost heater and thermistor, tested rather than assumed The evaporator and the drain line Stored codes, which say what the unit has been doing rather than what it is doing now After a power cut Storm season brings its own version of this: a freezer that came back up but never quite recovered, or one that restarted with the ice maker out of step. Worth checking the same week rather than the same season — a unit that is running but struggling is quieter about it than one that stopped. --- **[Read full article: Freezers](https://subzeromiami.support/appliances/freezer/)**