The short answer: when ice builds up inside a walk-in freezer, something in the system has stopped doing its job. In our experience it's almost always one of six things: the evaporator fan stopped, the defrost timer failed, the defrost heater or drain line failed, the system is low on refrigerant, the thermostat isn't working, or the door was left open. A little frost is normal. Thick ice on the coil, the pipes or the ceiling is not.
We've been repairing walk-in freezers across Toronto and the GTA since 2017. Here's what we find most often when a customer calls us about ice.
1. The evaporator fan stopped
The fan inside the freezer blows air across the coil. When it stops, the cold stays trapped on the coil and moisture freezes on it layer by layer. The reason isn't always the same: the motor may have failed, ice may be blocking the blade, or there may be a problem in the controls. We don't just swap the fan. We find out why it stopped, so it doesn't happen again.
2. The defrost timer went bad
Every freezer needs to defrost a few times a day to melt the light frost before it builds up. The defrost timer controls that. When the timer fails, the defrost never starts, and the frost keeps growing until the coil is covered.
3. The defrost heater burned out, or the drain line froze
Sometimes the timer works fine and the defrost starts on time, but nothing melts because the heater has burned out. A burned-out heater has to be replaced. There's no repairing it. Other times the ice melts, but the water can't get out because the drain line is frozen or blocked. It freezes again in the drain pan and builds up from the bottom. We check both on every iced-up freezer.
4. Not enough refrigerant
When the system is low on refrigerant, there's a leak somewhere. Only part of the evaporator gets cold, and ice builds up there while the freezer struggles to hold temperature.
Here's where we're different. We don't just add refrigerant and leave. The leak has to be found and fixed first. In Ontario, refilling a leaking system without repairing the leak isn't allowed, and it's money thrown away, because the gas ends up leaking out again. If we can't find the leak on that visit, we tell the customer honestly and explain exactly what we checked. We'd rather tell you the truth than charge you for gas that will be gone in a few weeks.
Read more: My freezer keeps needing refrigerant. Why we never just top it up
5. The thermostat isn't working
If the thermostat fails, the system doesn't know when to stop. It keeps running for hours, longer than it should, and ice builds up with it. You'll often notice the compressor never shuts off.
6. The door was left open overnight
This one happens more than people think. Someone leaves the door open at closing, warm, humid air pours in all night, and in the morning there's ice everywhere. Check the door closer and the gasket too. A door that doesn't seal properly does the same thing slowly.
What it looks like
By the time it looks like this, the system has been struggling for a while. Catching it early almost always means a smaller repair.
Please don't chip the ice off yourself
We understand the temptation, but don't break the ice with a knife, a screwdriver or a hammer. The coil is made of thin copper and aluminum, and one slip can puncture it. Then a defrost problem becomes a refrigerant leak and a much bigger repair. Leave the ice, keep the door closed, and call us.
Seeing ice in your freezer?
Don't wait for it to get worse. Ice makes the system work harder, raises your hydro bill, and usually ends with a breakdown and lost product. Call Tech Cooling at 416-655-7672. We repair all brands of walk-in freezers and coolers across Toronto and the GTA. 313A licensed, ODP certified.