When the system has power and air is moving but the air is not cold, stop and check a few safe items before a long runtime makes the problem worse. Acting early helps protect the compressor.
Check these before you call
- Thermostat: set to Cool, with a temperature below the room reading. Fan on Auto if you want to feel whether supply air is cold.
- Filter: a clogged filter can starve the evaporator coil, encourage icing, then send lukewarm air. Replace a dirty disposable filter.
- Outdoor unit: confirm the fan can spin and the sides are not packed with debris.
- Breakers and disconnect: confirm the outdoor disconnect and HVAC breaker have not tripped.
Common on-site causes
- Dirty evaporator or condenser coil
- Low refrigerant from a leak
- Failed capacitor or contactor
- Outdoor fan motor problems
- Clogged condensate drain that opens a float safety and cuts cooling
- Duct leaks or closed supply registers
If you see ice, shut it down
Ice on the copper lines or indoor coil is a signal to turn cooling off. Switch the fan to On to help thaw if the manufacturer allows fan-only operation. Running a frozen or low-charge system can damage the compressor.
Get it diagnosed
Request AC repair when home checks do not restore cold air. Related reading: reasons a house will not cool and cooling services.