Ice build-up in a freezer is easy to ignore, but it affects how well your freezer works. The answer to how often you should defrost a freezer depends on the type of freezer you have, and some modern freezers never need defrosting by hand.
This guide explains how often to defrost each type, why ice builds up too fast, how to defrost safely and when to call an engineer.
If you have a manual-defrost freezer, defrost it once or twice a year, or whenever the ice reaches around 5 mm thick. If you have a frost-free freezer, you should not need to defrost it by hand. Heavy ice in a frost-free freezer usually points to a fault, such as a worn door seal or a blocked drain.
Why Does Ice Matter?
A light layer of frost is normal. Thick ice is a problem for a few reasons.
- It acts like a blanket on the cooling surfaces, so the freezer has to work harder and run for longer.
- It can use more electricity.
- It takes up space, and it can stop doors and drawers from closing properly.
- It can block vents and drains and cause more serious faults.
How Often Should You Defrost a Freezer?
Freezer type |
How often to defrost |
| Manual-defrost upright or under-counter freezer | Once or twice a year, or when frost reaches about 5 mm |
| Chest freezer | At least once a year, ideally when stock is low, or sooner if the ice is thick |
| Frost-free (no-frost) freezer | Not normally needed. Defrost manually only if there is a fault or a blocked vent |
| Fridge freezer with auto-defrost fridge section | The fridge section defrosts itself, but check the drain hole regularly |
Check your manual, as manufacturers give their own advice. Many recommend defrosting when the ice is about 5 mm thick, although some say a little more.
Simple Checks to Try First
If your freezer is icing up quickly, check these before you defrost.
- Check the door seal: Close the door on a sheet of paper. If it pulls out easily, the seal may be worn, and warm air is getting in. Also check for cracks, gaps and dirt.
- Check the drain hole (fridge freezers): Look for the small drain hole at the back of the fridge compartment. If it is blocked by food, water can overflow and freeze. Clear it gently with a cotton bud or a thin plastic tool. Our guide on why your fridge is leaking water inside explains the drain in more detail.
- Check the temperature: A freezer is usually set at around -18°C. Colder than that is not needed and wastes energy.
- Check how it is packed: Do not pack food tight against the back wall or vents. Leave space for air to move around.
- Check the door: Make sure it is not left open, and that the freezer is level, so the door closes fully.
5 Common Reasons Ice Builds Up Too Fast
If your freezer gets heavy frost every few weeks, one of these is often the cause.
1. A Worn or Damaged Door Seal
The rubber seal stops warm room air from getting in. Over time, it can dry out, crack or split. When warm, moist air gets into the cold cabinet, the moisture turns to frost very quickly. Replacement seals are available for most models.
2. A Blocked Defrost Drain
In fridge freezers with a self-defrosting section, melted ice runs down a drain to a tray at the back of the appliance. If the drain is blocked by food or ice, the water can pool and freeze at the bottom of the cabinet.
3. A Faulty Defrost Timer or Control Board
Frost-free freezers use a timer or control board to start regular defrost cycles. If it fails, defrosting stops, and ice builds up on the cooling coils at the back. Airflow is then restricted, and food can begin to thaw.
4. A Failed Defrost Heater
Frost-free freezers have a small heater that melts the frost on the evaporator during a defrost cycle. If the heater fails, ice builds up in thick blocks. You may hear the fan hitting ice, which makes loud noises.
5. A Faulty Thermal Fuse or Sensor
A thermal fuse protects the defrost system from overheating. If it blows, the heater may lose power. A faulty temperature sensor can also give the control board wrong readings, so it does not start defrost cycles properly. These are not DIY jobs.
How to Defrost Your Freezer Safely
- Switch off and unplug: Turn the freezer off at the wall socket and unplug it.
- Empty the freezer: Move your food into cool bags or a cool box with ice packs, and keep it somewhere cool. Do not refreeze food that has fully thawed.
- Protect the floor: Put towels or a shallow tray around the base to catch water.
- Let the ice melt naturally: Leave the door open. To speed it up, place a bowl of warm (not boiling) water inside, and replace it as it cools. Use a fan to circulate air if you wish.
- Remove loose ice carefully: Use a plastic scraper or spatula. Never use a knife, ice pick or metal scraper, because you can puncture the cooling pipes and cause damage that cannot be repaired.
- Clean the inside: Wash with warm water and a little bicarbonate of soda or mild washing-up liquid. Rinse and wipe it clean.
- Dry completely: Dry all surfaces, because any water left behind will turn to fresh ice.
- Switch back on and refill: Plug the freezer in, let it get cold again (follow your manual) and then put the food back.
Defrosting can take several hours, sometimes overnight, depending on the amount of ice. Do not use a heat gun. It is also best to avoid a hairdryer, because heat can warp the plastic, and using electrical equipment near water is a safety risk.
When Should You Call an Engineer?
Defrosting is usually a simple job, but some problems need a professional.
You can do yourself:
- Wipe away water and loose ice with soft cloths.
- Clear a blocked drain hole gently.
- Check and clean the door seal.
- Check the temperature setting.
Leave to an engineer:
- Testing defrost heaters, thermal fuses and sensors with a multimeter.
- Replacing a defrost timer or control board.
- Repairing the cooling system or refrigerant leaks.
- Fixing a fan motor blocked by ice.
Call an engineer if:
- Heavy ice keeps coming back soon after you defrost.
- A frost-free freezer is icing up at the back.
- Food is thawing even though the freezer is running.
- The freezer makes loud clicking or grinding noises.
- The freezer runs constantly or trips your fuse box.
Frequently Asked Questions
How long does it take to defrost a freezer?
It can take a few hours, and sometimes overnight, depending on how much ice there is. Placing warm water inside can speed things up. Do not use a heat gun or a naked flame.
Why is my frost-free freezer building up ice?
Common causes are a worn door seal, a blocked drain or a faulty defrost heater, timer or sensor. A frost-free freezer should not normally need manual defrosting, so heavy ice is a sign to get it checked.
Can I use a hairdryer to defrost a freezer?
It is best not to. Heat can damage the plastic lining, and mixing water and electricity is dangerous. Let the ice melt naturally, with the help of warm water in a bowl.
What happens if I never defrost my freezer?
Thick ice makes the freezer work harder and use more electricity, takes up storage space and can block doors, vents and drains. In the long run, it can increase wear on the compressor.
Is it safe to keep food while defrosting?
Move it into cool bags or a cool box with ice packs, and keep it cold. Do not refreeze food that has completely thawed.
Need Help With a Freezer That Keeps Icing Up?
A freezer that ices up quickly is telling you something is wrong. Our trained and insured engineers cover all London boroughs and work on all major brands, with a guarantee on parts and labour.
If defrosting has not solved the problem, or the ice keeps coming back, book a visit for Freezer Repair in London and get honest advice and clear pricing. Contact London Appliance Repair now .