When the freezer is cold but the fridge side is warm, the refrigerator is making cold air fine; it just is not moving it. Most fridges cool one evaporator in the freezer and share air through vents and a damper. A failed evaporator fan, frost choking the vents, or a stuck damper starves the fresh-food side while the freezer stays cold.
Check the simple airflow blocks first
Look at the vents between the compartments, usually on the freezer's side or back wall. A bag of frozen vegetables parked against them can do this all by itself. Rearrange, give it several hours, and check the fridge temperature with a thermometer, aiming for 37 to 40 degrees. Also confirm no one set the fridge control colder to compensate; max cold settings can ice a damper shut.
While you are there, listen. With the freezer door switch pressed in, you should hear the evaporator fan run and feel air moving. Silence, or a fan that buzzes and stalls, is your first real suspect.
The frost pattern that gives it away
If the freezer's back wall wears a coat of frost, the defrost system has likely failed: heater, defrost thermostat, or control. Frost swallows the evaporator until air cannot pass, and the fridge side warms first. The 24-hour test from homeowner forums actually works here: empty the unit into coolers, unplug it, leave the doors open a full day, and restart. If it cools perfectly for a week and then fades, you have confirmed a defrost fault rather than fixed it, and that distinction saves you from replacing the wrong parts.
This is the point where social media advice usually goes sideways. A very common story online: an owner replaces the condenser or evaporator fan motor on a guess, the fridge still does not cool, and a technician later finds the defrost system was the fault all along. Testing the defrost chain takes minutes with a meter and beats buying parts in order of price.
When it is not airflow
A failed damper control, a drifting fridge thermistor, or a control board that will not call for the fan can mimic the same symptom with clean vents and no frost. So can a refrigerator installed tight into Bridgemore Village cabinetry with its condenser airflow strangled. If vents are clear, no frost is present, and the fan runs, the diagnosis moves to sensors and controls, which is meter work.
What it is almost never, in this exact pattern, is the compressor or refrigerant: a sealed system that keeps a freezer at zero has proven it can make cold. That is genuinely good news, because airflow and defrost repairs sit at the friendly end of the price range. Our refrigerator repair page walks the full process, and the before-you-call checklist shows what to photograph for us.