Why a display cabinet ices up
My display fridge keeps icing up at the back. Why does it happen and will it fix itself?
Published 18/09/2026. Written by the Pristine Cooling team, Kalgoorlie.
Ice at the back of a display cabinet is almost always moisture that is getting in faster than the defrost cycle can clear it. No, it will not fix itself. It gets worse, because ice blocks the airflow that was keeping the cabinet cold, so the unit works harder, runs colder at the coil, then freezes up faster than it did the week before. The good news is that the cause is usually something in the shop rather than something broken in the machine.
Here is what is actually going on, then the five things that cause it.
What is happening back there
The panel at the back of the cabinet hides the evaporator, which is the coil that does the cooling. It runs below freezing. Air from the cabinet passes over it, the moisture in that air condenses onto the cold fins, then freezes.
That is normal. Every refrigeration system does it. Which is why every one of them also has a defrost cycle: a few times a day the cooling stops, the ice on the coil melts, the water runs down into a tray, then out through a drain. Then the cabinet goes back to work.
A cabinet ices up when one side of that arrangement stops balancing. Either more moisture is arriving than the defrost was set up to handle or the melt water is not getting away.
1. It is loaded above the load line
The most common one by a distance.
An open front merchandiser works by pushing a curtain of cold air down across the opening. That curtain is what keeps shop air out. There is a line moulded or printed inside the cabinet showing how high stock can go without breaking it.
Stack a carton above that line or push product forward so it sits proud of the shelf edge. The curtain then gets deflected into the room instead of falling clean down the front. Warm shop air pours in to replace it, carrying all its moisture onto your evaporator. The cabinet is then doing a job it was never designed for, every hour it is open.
Restocking day is when this happens. It looks like a fault on Thursday because of what was put in on Wednesday.
2. The night blinds are not going down
If the cabinet has a blind, pulling it down at close is worth more than almost anything else on this list. Overnight is eight or ten hours of the cabinet either sealed or open to the room.
Blinds get left up because the last person out is in a hurry, because the blind is stiff or because nobody ever said it mattered. It matters.
3. The drain is blocked
This one gets misread as a defrost fault constantly.
The defrost works perfectly, the ice melts exactly as designed, then the water cannot get away. Drains block with wrapper film, label paper, sugar residue from a spill or from general gunk if the cabinet has not been cleaned out in a while. The water sits in the tray, the next cooling cycle starts, it freezes solid, then the next defrost has to melt both the new ice and the old.
The tell is water pooling in the base of the cabinet or ice forming low down rather than only on the coil.
4. The defrost is not set for this shop
Defrost frequency and duration are set when the cabinet is commissioned, against an assumption about how busy it will be.
Shops change. A cabinet moved near a doorway, a cabinet that used to be opened twenty times a day and is now opened two hundred, a cabinet that went from drinks to deli, is working in different conditions to the ones it was set up for. The settings are still the old ones. That is not a fault, it is a setting. It is also one of the quickest things to put right.
5. Door seals, on the glass door ones
Same story as any other door. Seals go hard, tear or get pulled out of shape by a trolley. A door that does not pull up tight leaves a gap that breathes shop air all day.
Worth running your hand around the closed door. If you can feel air moving, you have found it.
The one that catches people out
Humidity in the shop itself.
Mopping the floor at close and leaving it wet overnight puts a surprising amount of water into the air, right next to a cabinet that will spend the night pulling it out again. Same with a dishwasher or glass washer venting nearby, a roller door left up on a wet morning or a cool room door propped open across the aisle.
If the icing started when nothing about the cabinet changed, look at what changed around it.
The one thing never to do
Do not chip the ice off.
Not with a screwdriver, not with a knife, not with anything metal. The evaporator is thin aluminium fins wrapped around thin copper tube with refrigerant inside it. One good jab turns a defrost problem into a leak, which is a different job at a different price, on a cabinet that now has to be emptied.
If you need to clear ice yourself, turn the cabinet off, move the stock, then let it melt on its own. Warm water is fine. A hair dryer held well back is fine. Sharp metal is not.
What to do now
Work down the list. Load line, blind, drain, seals, then what changed around it. Most of the time it is one of those, it costs nothing to fix, then it stays fixed until the next restocking day teaches everyone the same lesson again.
If the cabinet is clear on all five and still icing, the defrost settings or the system itself need looking at, which is us. Our after hours line is for commercial sites. You do not need an account with us to ring it. The after hours call out is a flat fee with the first four hours of same day labour inside it, parts are quoted before anything is fitted, travel beyond 20km from our Boulder Road workshop is quoted before we book. The detail is on the 24/7 Breakdown and Repairs page.
You get a written report either way, which is the thing worth having if the cabinet is holding product you have to account for.
A cabinet that ices up on a cycle, clears, then does it again a month later is telling you something about how it is being used rather than about how it was built. That pattern is exactly what a maintenance visit is for, because the settings get checked against how the shop actually runs now. See what else we look after on the commercial refrigeration page.
Ring us and we'll tell you when we can be there
Same number either way. Ring it if something is down right now or if you want a quote, a service or a maintenance contract set up.