Heating & Cooling · Common problems · Updated November 2026
AC Running but Not Cooling: What to Check
If the fan is running but the air is not cold, start with the simple checks below. Many no-cool calls turn out to be a thermostat setting, a clogged filter or a tripped breaker for the outdoor unit.
In extreme heat, older adults, infants and people with health conditions are at risk. If the house is dangerously hot, move to a cooler place while you wait for repairs.
Check these first
- Thermostat is set to "cool" and below room temperature; fan set to "auto."
- Air filter is clean.
- The outdoor unit is running. If not, check the breaker and the outdoor disconnect switch (reset a tripped breaker once only).
- The outdoor unit is clear of leaves, grass and plants, with about two feet of space around it.
- Supply vents are open.
Common causes a technician finds
- Frozen evaporator coil: from low airflow or low refrigerant. Ice on the lines is a clue; turn the system off to thaw.
- Low refrigerant: means there is a leak that needs to be found and fixed.
- Failed capacitor or contactor: the outdoor fan or compressor will not start.
- Dirty outdoor coil: the unit cannot release heat.
- Clogged condensate drain: some systems shut off cooling when the drain backs up.
When to call a pro
Call if the simple checks do not fix it, the breaker trips again, or you see ice. Ask whether repair or replacement makes more sense if the system is older (AC repair vs. replacement).
Cost figures are national ranges from the sources listed in our heating & cooling cost guide, not a quote from FixFinch or any contractor. This article is general information to help you decide on next steps. It is not an inspection or professional advice; a qualified pro who sees the problem in person can tell you what is actually going on. Calls connect you with an independent service provider in our network. FixFinch is not a contractor and does not perform the work.