Refrigerator Not Cooling: Coils, Fan, or Defrost System
Work from the outside in. The most common cause is also the easiest to fix, and people go straight to assuming a dead compressor.
1. Condenser coils
Dust and pet hair blanket the condenser coils, the fridge cannot reject heat, and cooling performance falls off. This is the single most common cause of poor cooling and the most neglected maintenance item in a kitchen.
Unplug the fridge. The coils are behind a grille at the bottom front, or on the back panel on older units. Vacuum them with a brush attachment and a coil brush.
Do this every six months, and every three if you have shedding pets.
2. Condenser fan
Same location. With the fridge running, the condenser fan should be spinning whenever the compressor is. If it is stopped, obstructed, or grinding, the compressor overheats and cycles off on thermal protection — which produces exactly the “runs but does not cool” symptom.
Unplug, clear any debris, and spin the blade by hand. Stiff or noisy means the motor is failing.
3. Evaporator fan and airflow
The evaporator is inside, usually behind a panel in the freezer. Its fan pushes cold air into the fresh food compartment.
Symptom that points here: freezer is cold, fridge is warm. The cold is being made but not moved.
Open the freezer and listen. You should hear the fan; opening the door usually stops it (there is a door switch). If you never hear it, suspect the fan motor or its switch.
Also check the simple things: vents blocked by food, and a fridge packed so full that air cannot circulate. Cold air needs a path.
4. Frost on the evaporator — the defrost system
Remove the freezer’s rear panel. The evaporator coil should have light, even frost. If it is buried in a solid block of ice, the defrost system has failed and the ice is blocking all airflow.
Three parts can cause it:
- Defrost heater — an element that melts frost periodically. Test for continuity.
- Defrost thermostat or bi-metal — tells the heater when to run.
- Defrost timer or control board — schedules the cycle.
You can confirm the diagnosis by unplugging the fridge for 24–48 hours with the doors open to melt the ice completely. If it cools normally afterwards and then degrades again over a week or two, the defrost system is the fault.
5. Door seals
Run a sheet of paper through the closed door. If it pulls out with no resistance anywhere along the seal, the gasket is leaking, and a leaking gasket both raises the temperature and frosts the evaporator.
Gaskets are replaceable and often clip or screw in. Clean them first — they sometimes just need warm soapy water and a wipe of petroleum jelly to seal again.
6. Temperature and placement
- Set point: 37–40 °F (3–4 °C) fridge, 0 °F (-18 °C) freezer.
- Clearance: a few inches at the back and sides. Fridges built into tight cabinetry without airflow struggle in summer.
- Ambient: a fridge in an unheated garage may stop cooling in winter, because the thermostat senses a cold room and never calls for cooling.
Where it stops being DIY
Anything in the sealed refrigerant circuit — compressor, refrigerant charge, capillary tube, evaporator leaks — requires certification to work on legally in most jurisdictions, and specialist equipment. Symptoms: the compressor is hot and humming but never starts, or it runs continuously and nothing gets cold with clean coils and working fans.
At that point, weigh the repair against replacement. A sealed-system repair on a ten-year-old fridge is usually not worth it.
Narrowing it down by which compartment is warm
The split between the two compartments is the fastest diagnostic shortcut, since a fridge makes all its cold in one place and distributes it.
| Freezer | Fridge | Points at |
|---|---|---|
| Cold | Warm | Evaporator fan, damper, or air duct blocked with ice |
| Warm | Warm | Condenser coils, condenser fan, compressor, or refrigerant |
| Warm | Cold | Unusual; sensor or control fault |
| Cold, ice building | Warm | Defrost system failed |
That table saves opening panels in the wrong order.
The damper and the thermistors
On most modern fridges, a motorised damper controls how much cold air passes from the freezer into the fresh food compartment. If it sticks closed, the freezer is fine and the fridge is warm — with the evaporator fan running normally.
The damper is usually behind a panel in the top rear of the fridge compartment. You can often hear it move when the control calls for cooling.
Thermistors are small temperature sensors, and a drifted one makes the control board act on wrong information. If the fridge holds a steady but wrong temperature, and coils and fans are all healthy, a thermistor is a likely and inexpensive cause. They are tested by resistance against a temperature chart for the model.
Listening as a diagnostic
Each sound tells you something specific:
- A steady low hum from the back — compressor running. Good.
- A click every few minutes, then nothing — the start relay is trying and the compressor is not starting. A start relay is a cheap part and a common failure; a compressor is not.
- Loud buzzing or rattling from the back — condenser fan blade hitting something, or a loose mount.
- A whirring that changes when you open the freezer door — evaporator fan working normally.
- Gurgling or popping after the compressor stops — refrigerant and defrost water. Normal.
- Nothing at all, with the light on — the compressor is not being commanded to run. Control board, thermistor, or start relay.
Ice in the wrong places
Ice on the freezer floor or in a puddle under the crisper drawers is a blocked defrost drain. Melt water from each defrost cycle should run down a tube to a pan above the compressor, where it evaporates. When the tube blocks with debris or freezes, the water finds another route.
Clearing it means locating the drain hole at the base of the evaporator compartment and flushing it with warm water and a length of flexible tubing. It is a satisfying fix and it recurs if the tube’s heater or its routing is at fault.
Frost on the interior walls of the freezer points at a door seal or a door left ajar, letting humid air in.
Deciding whether to repair
A rough rule: if the repair costs more than half the price of a comparable new unit and the fridge is past eight years old, replace it. Sealed-system work almost always crosses that line.
Two things push the other way: a good-quality unit with a documented failure of one cheap part (start relay, defrost heater, fan motor) is worth fixing, and a built-in or counter-depth model is expensive enough to replace that repair economics change completely.
Before deciding, clean the condenser coils and check both fans. A surprising number of “dying” fridges are simply choked with dust.