AC Not Cooling But Running: Diagnosis & Repair Costs 2026

Who this is for: Homeowners whose AC is running right now but blowing warm or barely-cool air, who need to know in the next 10 minutes whether this is a $0 fix, a $400 service call, or a sign the system is finished.

If your AC is running but not cooling, the cause is almost always one of seven things — and four of them you can diagnose yourself in under ten minutes. The most common culprit in 2026 service data is a clogged air filter restricting airflow across the evaporator coil, followed by low refrigerant from a slow leak. If your unit is over 12 years old and this is the second cooling-related repair in 18 months, the math almost always favors replacement over repair.

An air conditioner has one job: move heat from inside your house to outside. When it runs but doesn't cool, that heat-transfer cycle has been broken at one of four points — the air handler (indoor), the evaporator coil, the refrigerant lines, or the condenser (outdoor). The compressor may sound fine and the fans may spin normally even when the system has lost the ability to actually transfer heat. That's why "running" and "cooling" are two separate problems.