Samsung’s upright freezers, sold under the RZ prefix and, in the current line, convertible between freezer and refrigerator duty, are single-door columns with one evaporator behind a rear cover, one fan, a defrost heater and sensor and an inverter compressor below. That simplicity is useful for diagnosis: with only one cooling circuit, a problem shows up quickly and completely. The commonest complaint is frost, a growing sheet of it on the back panel, and it is worth understanding what the frost is saying before the freezer is written off.
Frost Means Defrost Has Stopped or Been Overwhelmed
The evaporator behind the rear cover frosts in normal use, and several times a day the compressor pauses while a heater melts that frost and the water runs to a pan over the compressor. When frost reaches the rear panel and the drawers, one of two things has happened: the defrost cycle has stopped, because the heater, its sensor or the control timing them has failed, or the cycle is running but cannot keep up with moisture arriving through a door that does not seal. The second is far more common and far cheaper.
The Door First
An upright freezer door is opened many times a day and is easily left ajar by a drawer that was pushed in crooked or a bag of frozen vegetables wedged against the liner. With the door closed, run a strip of paper around the gasket at several points; it should drag as you pull it. Look for a gasket split at the corners, or flattened where the door is pushed shut against an overfilled drawer. Check the door is not hitting a nearby cabinet before it seals. A freezer that has been leaning back slightly closes on its own; one that leans forward stays ajar, so check it stands level or tilts a little back. If the door alarm has been sounding, take that as the gasket check done for you.
The Manual Thaw
With the freezer switched off and unplugged and its contents moved to another freezer or a cooler with ice, leave the door open with towels on the floor and let it thaw completely, which for a heavily frosted evaporator can take most of a day. Do not scrape the rear panel or the evaporator with metal; the panel is plastic and the evaporator behind it is aluminum tubing that punctures easily, and a punctured evaporator is a sealed-system repair. Dry the interior, plug it in, let it run empty for a few hours until it reaches temperature and only then reload. If the frost returns to the same thickness within a couple of weeks with a good door seal, the defrost circuit has failed and the freezer needs the rear cover off and the heater and sensor tested, which is a visit.
The Convertible Mode
The current RZ models can be set from the panel to run as a refrigerator instead of a freezer. The hardware does not change; only the temperature the control aims for does. Two things follow. First, a freezer set to refrigerator mode by accident, easy to do while cleaning the panel, will hold its contents at refrigerator temperature and thaw them, with no code shown; check the mode before assuming a problem. Second, a cabinet switched from freezer to refrigerator mode while heavily frosted will drip for hours as the evaporator clears; that is not a leak.
Food Safety During All of This
A freezer that has been running warm because of frost, or that has been thawed for a defrost, needs a thermometer, not a look. Frozen food that reads 40°F or below or still holds ice crystals can be refrozen or cooked; anything that has been above 40°F for two hours or more should be discarded, following the FDA guidance. Do not judge by whether a package has refrozen. If the freezer holds temperature after a thaw and a door check, no visit is needed; if it does not, book a Samsung freezer repair with the model number from the label inside the door.