Why does my fridge freezer run constantly?
A compressor that never stops is either shedding heat badly, being fed warm air, or being asked for a colder temperature than it needs — and all three are things you can check in an hour.
- Difficulty
- beginner
- Time
- 45 min
- Read
- 4 min
- Safety
- caution
Short answer
Check the condenser coils for dust, the clearances behind and above, the door seals, and the temperature setting. A healthy appliance runs roughly a quarter to a half of the time. If it runs constantly and is still cold, work through those four. If it runs constantly and is not cold, it is losing capacity and needs an engineer.
Constant running is not automatically a fault: a hot kitchen, a big shop just put away, a warm summer week or a nearly empty appliance will all keep a compressor going for long stretches. It becomes a problem when it is the new normal, because it means the appliance is working at the edge of its capacity all the time — which shows up in the bill and shortens its life.
Safety
What you'll need
- A fridge thermometer
- A vacuum with a brush attachment
- A sheet of paper for the seal test
- A torch (optional)
Step by step
- Confirm it is actually running constantly.Listen at intervals across an evening rather than judging from one moment. A normal duty cycle is roughly 25-50% depending on the season and the appliance. Genuinely constant means no quiet periods at all across several hours.
- Check whether it is still holding temperature.Thermometer in the fridge and one in the freezer. Cold and constantly running is an efficiency problem. Warm and constantly running is a capacity problem and much more serious.
- Unplug it and clean the condenser coils.Black grille at the back, or a grille behind the plinth on models with a base-mounted condenser. Brush and vacuum the dust off. This is the biggest single cause and the most neglected job on any cold appliance — dust is an insulator, so the heat cannot leave.
- Restore the ventilation clearances.Pull it forward so there is a gap behind, clear anything stored on top, and check nothing has fallen down the back against the coils. On an integrated appliance, check the plinth vent and the outlet at the top of the housing are both clear.
- Run the paper test on every seal.Both doors, all the way round. A failed seal means the appliance is cooling the kitchen continuously. Clean the seals first — a sticky or dirty gasket does not compress properly and can pass the test after a wash.
- Check the temperature setting is not colder than it needs to be.A fridge holding 2°C rather than 5°C runs substantially harder for no safety benefit. Set it by measurement rather than by dial number, and give the appliance 24 hours to settle before judging any change.
- Check what the appliance is being asked to do.A large warm shop, hot leftovers put in, a fast-freeze function left on, or a door opened constantly by children will all keep it running for hours. Fast freeze in particular disables the thermostat on many models and must switch off, or be switched off, afterwards.
- Check the room temperature.An appliance next to an oven, in a conservatory, in direct sun or in a kitchen above its climate class maximum will run continuously in summer. This is the appliance being overwhelmed rather than faulty.
- Check for ice on the freezer rear panel.On a frost free appliance, an iced evaporator blocks airflow, so the cabinet stays warm and the compressor never stops. A full manual defrost that fixes it for a few weeks confirms a defrost circuit fault.
- Call an engineer if it runs constantly and cannot hold temperature.After the coils, clearances, seals and settings are all right, an appliance that still cannot reach temperature has lost capacity — a refrigerant leak, a failing compressor or a fan fault. Those are diagnoses rather than adjustments.
Common mistakes
- Turning the thermostat warmer to make it run less — It will run less and the food will be less safe. Set the fridge by measurement to 5°C or below and fix the reason it is struggling instead.
- Never cleaning the condenser coils — It is the single highest-value maintenance job on a cold appliance, it takes ten minutes once a year, and a heavily dusted condenser can add a meaningful amount to the running cost while shortening the compressor's life.
If it doesn't work
Runs constantly, still cold, bill has crept up
Cause: Dusty condenser, blocked ventilation or a tired door seal — Fix: Clean the coils, restore clearances, test and clean the seals. These three together account for most cases.
Runs constantly since a hot spell started
Cause: Ambient temperature at or above the appliance's climate class limit — Fix: Improve ventilation, shade the appliance from direct sun, and move it away from any heat source. It should settle when the weather does.
Runs constantly and neither compartment is cold enough
Cause: Loss of refrigerant, compressor wear, or a blocked evaporator — Fix: Engineer diagnosis. Move the food somewhere safe rather than waiting to see whether it improves.
Started after a big shop or a batch cook
Cause: The appliance is doing its job — Fix: Give it 24 hours. If it settles back into a normal cycle, nothing is wrong.
Questions people ask
How often should a fridge freezer actually cycle?
A rough guide is on for 10-20 minutes and off for 20-40, giving a duty cycle somewhere between a quarter and a half. It varies enormously with the season, how full it is and how often the door opens, so judge it over a day rather than an hour.
Is constant running dangerous?
Not dangerous, but it is expensive and it wears the compressor. An appliance that has been running constantly for months is more likely to fail than one cycling normally, which is a reason to find the cause rather than live with it.