A walk-in freezer should hold at 0 F or colder, and most are set somewhere between zero and minus 10. When one starts drifting above zero, ice cream goes soft first. Around the same time you’ll usually find frost or ice somewhere it doesn’t belong, and the spot where it’s building up is a good clue to what failed.
Reading the ice
Ice packed solid in the evaporator coil, with the fans pushing against a white wall, usually means defrost isn’t working. The heater may have burned out, or the timer or controller stopped calling for defrost. A termination sensor that ends the cycle too early does the same thing.
Ice on the floor under the evaporator, or icicles hanging off the bottom of the unit, points at the drain. Freezer drain lines have a heater wrapped around them because the meltwater would refreeze in the line otherwise. When that heater fails the line plugs, and the pan overflows onto whatever’s below and freezes there.
Frost on the ceiling and walls near the door means moist air is getting in, usually through a torn gasket or a door that stays open during deliveries (a missing strip curtain makes that much worse). Ice in the door frame itself is more often the frame heater wire, which keeps the frame just warm enough that the gasket can’t freeze to it.
How a freezer defrosts
A cooler can melt its frost with box air because the air inside is above freezing. A freezer can’t, so it uses electric heaters built into the evaporator coil (some bigger systems use hot gas from the compressor instead). A few times a day the controller shuts off the compressor and fans and turns the heaters on. When the coil is clear, a sensor ends the cycle, and there’s a short delay before the fans restart so they don’t spray water around the box. Any one of those parts can fail, and from the outside it all looks about the same: a coil that gets a little icier every day until the box can’t hold zero.
If you’re trying to tell a small icing problem from a big one, we wrote a longer piece on freezer icing, small fix or big repair.
Doors that stick or won’t seal
When the frame heater quits, the gasket freezes to the frame and people start yanking on the door until the gasket tears. Then warm air leaks in and frost builds up around the opening, which makes the sticking worse. Replacing the heater wire and the gasket together is a common fix.
Most freezers also have a small pressure relief port in the wall. Shutting the door traps warm air that then cools and shrinks, which pulls a slight vacuum, and the port lets air back in so the door opens normally. If the port’s heater fails and it ices shut, the door can be really hard to pull open for a minute or two after it closes, and people tend to assume the door itself is broken.
While you wait
Keep the door closed. A full freezer holds temperature a lot longer than a cooler, especially if nobody’s going in and out. Log the temperature with the time every hour or so. Product that’s still frozen hard is usually fine. If things have started to soften, decide what to keep based on temperature and how long it’s been, and ask your health inspector if you aren’t sure. Our page on product loss and insurance covers the paperwork side.
Don’t hack at the ice with a knife, and don’t pour hot water into the coil. Both can puncture tubing or soak the fan motors.
On the visit
The tech checks the defrost heaters, the timer or controller, the termination sensor, the fan delay, the drain heater and the door heaters, along with refrigerant pressures and the condensing unit. Freezer compressors work harder than cooler compressors, so a dirty condenser hurts more here. Sometimes a coil has to be thawed out before the system can be tested properly. If so, the tech will tell you how long that takes and what it means for your product.
If a freezer quitting over a weekend would really hurt, an alarm that texts someone when the box warms up is a good idea. Our page on temperature monitoring has more on that. And if your cooler’s acting up too, the walk-in cooler page covers the differences.
