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Not cooling
What is going on
The system runs but the house does not cool, or the outdoor unit does not start.
Likely causes
- 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
Check in this order
- 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
Applies to: Central air conditioners
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Source: General HVAC service practice — verify per model. Written in our own words; check the manual for your exact model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.