Why is my freezer not freezing when the fridge is still cold?

In most fridge freezers one cooling surface serves both compartments, so a fridge that is still cold while the freezer is not points at airflow, ice or the fan — not at a dead compressor.

Difficulty: beginner
Time: 1 hr
Read: 5 min
Safety: warning

Short answer

On a frost free appliance, the usual cause is the evaporator behind the freezer's rear panel iced solid, or its fan failed, so cold air is no longer being moved. On a static appliance, check the freezer door seal and whether anything is blocking the vents between the compartments. Move the food somewhere cold before you investigate.

This symptom confuses people because it looks like half the appliance has died. In fact most fridge freezers have a single sealed system and a single evaporator, usually in the freezer, with cold air ducted or leaked into the fridge. The fridge often stays cold longest precisely because it only needs to be at 5°C. So a warm freezer with a cold fridge almost always means the cold is being made but is not reaching the freezer compartment properly, or is being lost from it.

Safety

Deal with the food first. Anything that has fully thawed and risen above 8°C for more than two hours must be thrown away — not refrozen and not cooked. Items still hard with ice crystals throughout can be refrozen, with a loss of quality. The sealed refrigerant circuit is never an owner job at any stage of this.

What you'll need

A freezer thermometer
A cool bag or somewhere to put the food
A sheet of paper for the seal test
A torch (optional)

How cold moves around a fridge freezer, and where the zones are

Step by step

Deal with the food before anything else.Anything still solid with ice crystals throughout is safe and can be refrozen once the appliance recovers. Anything soft, thawed and above 8°C for more than two hours goes in the bin. Move what you are keeping to a neighbour's freezer or a cool bag with ice packs.
Measure the actual temperature rather than judging by feel.A freezer thermometer left in for a few hours. -18°C is correct; -10°C is failing; anything above -6°C means the contents are deteriorating and only very short-term storage is safe. This tells you how urgent the rest is.
Check the freezer door seal and the door itself.Paper test all the way round. Then check nothing inside is holding the door off — an overfilled drawer or a bag caught in the opening is a very common cause of a compartment that will not hold temperature.
Check the vents between the compartments are not blocked.On many appliances there are ducts or a damper carrying cold air from the freezer to the fridge, or vents inside the freezer where the air enters. Packing food hard against them stops circulation, and the compartment furthest from the source suffers first.
Listen for the evaporator fan on a frost free appliance.Open the freezer and press the door switch by hand if there is one. You should hear a fan running behind the rear panel. Silence, or a rattling or grinding noise, points at a failed fan or a fan blade jammed by ice — and a stopped fan produces exactly this symptom.
Look for ice on the rear panel of the freezer.A solid sheet of ice across the back of a frost free freezer means the evaporator behind it has iced up and airflow has stopped. That is a defrost system fault: heater, thermostat or timer.
Do a full manual defrost as both a test and a temporary fix.Empty it, switch it off at the socket, and leave the doors open for 24 hours with towels down. If the freezer then works normally for a few weeks and fails again, you have confirmed a defrost fault and it needs an engineer. Never use anything sharp to speed it up.
Check the condenser coils and the ventilation around the appliance.Unplug it, pull it out and vacuum the coils at the back or underneath. A heavily dust-blanketed condenser reduces the whole system's capacity, and the freezer — which needs the biggest temperature difference — is the first compartment to suffer.
Check whether the appliance is in a cold room.In an unheated garage or utility room below the appliance's climate class minimum, the thermostat is satisfied by the ambient and the compressor barely runs, so the freezer drifts warm. This is a very common winter cause and it is not a fault in the appliance.
Call an engineer for the fan, defrost circuit or sealed system.An evaporator fan, defrost heater, defrost thermostat or control board is a repairable component fault worth quoting for. Loss of refrigerant is a sealed system fault and on a domestic appliance it usually ends it.

Common mistakes

Turning the thermostat colder and waiting — If air is not circulating or the evaporator is iced, a colder setting changes nothing except how long the compressor runs. Meanwhile the food keeps deteriorating.
Refreezing food that softened, because it looks and smells fine — Bacteria multiply well before food shows any sign. The rule is time and temperature, not appearance: above 8°C for more than two hours means throw it away.

If it doesn't work

Freezer warm, fridge cold, ice sheet on the freezer rear panel

Cause: Evaporator iced over — the defrost system is not clearing it — Fix: Full manual defrost to recover it, then have the defrost heater and thermostat checked. It will recur otherwise.

Freezer warm, fridge cold, no fan noise from the freezer

Cause: Evaporator fan failed or jammed — Fix: An engineer job, and usually an inexpensive part. Cold is being made and not moved.

Both compartments gradually warm, compressor running constantly

Cause: Blocked condenser, poor ventilation, failed seal, or refrigerant loss — Fix: Clean the coils and check clearances and seals first. If nothing improves after 24 hours, it is a sealed system diagnosis.

Started when the weather got cold, appliance in a garage

Cause: Ambient below the appliance's climate class minimum — Fix: Not a fault. Move it somewhere warmer or replace it with a garage-rated appliance — a standard freezer cannot hold -18°C in a cold garage.

Questions people ask

Can the fridge and freezer really share one cooling system?

Yes, on most fridge freezers. One compressor and usually one evaporator, with air ducted or a damper controlling how much cold reaches the fridge. It is why a fault in the airflow shows up as one compartment failing and not the other.

How long can I leave it before the food is unsafe?

Food stays safe while it remains frozen. Once it thaws, the two-hour rule above 8°C applies. If the freezer is at -10°C, the food is still frozen but degrading, so move it or use it rather than treating it as an emergency.