If the inside light turns on but your food is warm, the fridge has power — so it's not a dead outlet or a tripped breaker. That's the whole point of the light: it's on its own circuit from the door switch, so a working light only rules out an electrical problem, nothing else. The real cause is almost always one of five things below, and the pattern of what's warm and what you can hear tells a technician which one before any panel comes off.
Fridge Not Cooling But Light Is On: Short Answer
In order of how often we actually find it on service calls: (1) condenser coils caked in dust so heat can't escape, (2) a frozen-over evaporator coil or a jammed evaporator fan behind the freezer's back panel, (3) a failed start relay or capacitor that won't let the compressor kick on, (4) a bad thermostat or temperature sensor that never tells the compressor to run, and (5) a refrigerant leak, where the compressor runs constantly but nothing gets cold. The first two are the most common by a wide margin and the cheapest to fix — sometimes free. The full breakdown, with the sounds and symptoms that separate them, is below.
1. Dirty condenser coils
The coils on the back or underneath the fridge dump the heat pulled out of the food compartment into the room. Caked in dust, pet hair, and — in a lot of Orange County kitchens — the fine grit that blows in during Santa Ana wind season, they can't release heat fast enough. The compressor runs nearly nonstop trying to keep up, and the inside still drifts warm. What it sounds like: a compressor that runs far longer than normal, or seems to never cycle off. What to check: pull the fridge out (or open the bottom kick-plate grille on a built-in), and vacuum the coils and the area around them. Give it 4–6 hours after cleaning before judging the result — if that fixes it, you just saved yourself a service call. We recommend cleaning coils about once a year if you have pets; it's the single most common thing that turns into a "no-cool" call that didn't need to be one.
2. Frozen-over evaporator coil or a jammed fan
Behind the back panel inside the freezer sits the evaporator coil and a fan that pushes cold air forward into the fresh-food section. Refrigerators run an automatic defrost cycle a few times a day to keep frost from building up on that coil; when the defrost heater, the defrost thermostat, or the timer/control board fails, frost keeps accumulating until it either blocks airflow through the coil or physically jams the fan blade. What it sounds like: a faint buzzing, rattling, or clicking from inside the freezer wall — that's the fan blade catching on ice with every rotation. The tell: freezer runs warm too, not just the fridge, and you may see frost buildup around the back wall or vents if you look inside the freezer. This is a same-day repair — we thaw the coil, then test and replace whichever defrost component actually failed so it doesn't just refreeze in a few weeks. Parts and labor typically run $180–$320.
3. Failed start relay or capacitor
The compressor needs a jolt of extra current from a small start relay (and on some models a start capacitor) to get spinning. When the relay fails, the compressor tries and can't start — you'll often hear it click, hum for a second, and shut off, repeating every few minutes as the overload protector kicks it off each time to prevent it from burning out. What it sounds like: a rhythmic click-hum-click from the compressor compartment at the back or bottom of the unit, roughly every 2–3 minutes. This one's a straightforward same-visit repair on almost every brand — the relay is a small, inexpensive part — typically $120–$220 including labor.
4. Bad thermostat or temperature sensor
Modern fridges use a thermistor (a temperature sensor) that reports the inside temperature to the control board, which then decides when to run the compressor and fans. If that sensor fails or drifts out of calibration, the board never reads "too warm" and never calls for cooling — even though every other system in the fridge is working fine. The light staying on and the fans running normally is actually a clue here: it confirms the board has power and is operating, it's just not getting (or trusting) the temperature signal. A technician confirms this by checking the sensor's resistance against the manufacturer's chart at a known temperature. Replacement is usually $130–$230 and about 30–45 minutes, since the sensor is normally accessible without pulling the whole back panel.
5. Refrigerant leak (compressor runs constantly, nothing gets cold)
If the compressor is humming away continuously — not cycling, not clicking, just running — and the fridge still won't get cold, a slow refrigerant leak is the most likely explanation, especially on units past 10 years old where a fitting or the evaporator itself has corroded through. What it sounds like: normal, healthy compressor operation, which is exactly what makes this one confusing — everything sounds fine except the temperature. This isn't a DIY fix: finding a refrigerant leak needs an electronic leak detector or a dye-and-UV-light check, and recharging the sealed system legally requires EPA 608 certification. We pressure-test the system, locate and repair the leak, then evacuate and recharge to spec. Sealed-system repairs are the most expensive category here, generally $300–$600 depending on where the leak is and whether the compressor itself needs replacing.
What a technician checks, in order
- Confirms what's actually warm. Fridge only, freezer only, or both — this alone narrows the five causes above before any tool comes out.
- Pulls the unit and inspects the condenser coils for dust buildup, and checks that the condenser fan spins freely.
- Opens the freezer back panel to check for frost buildup on the evaporator coil and confirm the fan blade turns freely.
- Listens to and tests the compressor's start circuit — a clicking, cycling compressor points at the relay; a silent one at the board or wiring; a continuously running one moves the diagnosis toward the sealed system.
- Checks the thermistor's resistance against spec if the fans and compressor both check out electrically healthy but the board isn't calling for cooling.
- Pressure-tests the sealed system only after the cheaper, more common causes above are ruled out — it's the last step, not the first guess.
Is it worth repairing or should I replace it?
As a rule of thumb: under 8 years old, repair almost always makes sense — coils, fans, relays, and sensors are all inexpensive parts relative to a new fridge. Past 10–12 years, a major compressor or sealed-system repair is worth comparing against replacement cost, especially on a basic freestanding unit. On premium built-ins the math tips the other way — see our note on Sub-Zero units not cooling, which are engineered to be repaired for decades rather than replaced. And if the fans and compressor sound completely healthy but it's still not cooling, don't assume the worst before a diagnosis — see our guide on LG compressor failure for one specific, well-known case where the fix is often covered under warranty. Our techs give you the actual number upfront before doing any work, standard $95 diagnostic fee waived if you go ahead with the repair. Two more causes worth knowing if the fridge is running but not cold enough: a frozen-over evaporator from a failed defrost heater or thermostat (freezer stays cold, fridge side goes warm), and a scaled ice maker fill valve on hard Orange County water — both covered in more depth on our Mission Viejo refrigerator repair page, or see the OC-wide refrigerator repair breakdown for ice maker, leaking, and noisy-compressor cases not covered above.