A light layer of frost on the evaporator coil is part of how a freezer works. Moisture in the air freezes onto the coil, the defrost cycle melts it off a few times a day, and the water runs down the drain. Trouble starts when one piece of that stops working, or when more moist air gets into the box than the system can handle.
So start by looking at where the ice is. You can do that yourself in a minute, and it narrows things down a lot.
Ice around the door frame
Frost or ice on the door edges, the frame, or the first few feet of ceiling inside means warm, humid air is leaking in. Usually that’s a torn or flattened gasket, a door that doesn’t close all the way because the closer or hinges have worn, or a strip curtain that’s missing or torn up. Freezer doors also have a small heater wire running in the frame to keep the gasket from freezing to the metal. When it burns out, the gasket sticks, tears when someone yanks the door, and now you’ve got a gap. If your door has gotten hard to open, that heater is a likely suspect.
A gasket or a door closer is one of the cheaper freezer repairs.
A frozen puddle under the coil
Ice on the floor under the evaporator, or a drain pan full of solid ice, usually means the drain line is frozen. Freezer drain lines have their own heater because the defrost water would freeze on the way out otherwise. If that heater fails, the line plugs, the pan overflows on the next defrost, and the water freezes where it lands.
It’s a middle-size repair. The tech has to thaw the line and pan, replace the heater and check that the line still has the right slope. Don’t leave it, though, because that ice keeps growing and can creep up into the coil.
The coil is a solid block of ice
When you can’t see the fins on the evaporator coil because they’re buried in ice, air can’t pass through, and the box warms up even though the system runs nonstop. Roughly from simpler to bigger, the usual causes are:
- A defrost heater has burned out.
- The defrost timer or control has failed, or someone changed its settings.
- An evaporator fan motor has stopped.
- The system is low on refrigerant, often because of a leak.
A heater, timer or fan motor is an ordinary repair. A leak takes more, since it has to be found, fixed and tested before the system is recharged. And don’t let an iced coil sit for weeks. Refrigerant may not fully boil off in a coil that’s packed with ice, and liquid getting back to the compressor can damage it.
What not to do while you wait
Please don’t chip at the coil with a knife, screwdriver or ice pick. The tubes and fins are thin, and one slip makes a refrigerant leak out of what may have been a burned-out heater. Skip the heat gun too.
Move what you can into another freezer, keep the door closed, and call. The tech will usually do a controlled defrost and then test each part of the defrost system. It helps if you can tell us when you first noticed the ice and where it is, so the right parts come along on the visit.
Our walk-in freezer repair page has more on what a visit involves, and the same causes apply to reach-in freezers on a smaller scale. If the tech finds a leak, you’ll have a written price for the leak repair before any work starts. And if the unit is old enough that the repair gives you pause, read our guide to repair or replace first.
