Air Conditioner: Not cooling
Not cooling on a air conditioner: The system runs but the house does not cool, or the outdoor unit does not start.
Applies to: Central air conditioners
Common causes of not cooling
- Dirty filter or evaporator coil
- Dirty condenser coil
- Failed capacitor or contactor
- Low refrigerant charge or a leak
- Tripped breaker or disconnect
- Frozen evaporator coil
How to fix not cooling: step by step
- Confirm thermostat is in Cool and set below room temperature
- Replace the filter and check the indoor blower runs
- Check that the outdoor unit runs: breaker, disconnect, contactor, capacitor
- Clean the condenser coil
- Measure supply and return temperature split
- If the coil is frozen, shut down to thaw before checking charge
- Check superheat and subcooling against the manufacturer's charging chart
If the unit shows an error code, look it up: Carrier Air Conditioner codes Goodman Air Conditioner codes KeepRite Air Conditioner codes Lennox Air Conditioner codes Trane Air Conditioner codes
Source: General HVAC service practice — verify per model. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.