AC Not Cooling? 7 Fixes to Try Before Calling a Technician
By EasyToFix Homes Team
The air conditioner is running, but the house keeps getting warmer. Before you pay for a service call, know that most no-cooling problems come down to a handful of simple causes you can check yourself in under an hour. Work through these seven fixes in order.
1. Check the thermostat settings
Make sure the thermostat is set to COOL and the temperature is set below the current room temperature. It sounds obvious, but dead batteries, an accidental switch to HEAT, or a schedule override cause a surprising number of no-cooling calls.
If the thermostat screen is blank, replace the batteries. If it is a smart thermostat, check that it has Wi-Fi power and is not stuck in an eco hold.
2. Replace a dirty air filter
A clogged filter chokes airflow, which can freeze the evaporator coil and stop cooling entirely. Hold the filter up to a light: if you cannot see light through it, replace it.
Standard 1-inch filters need replacing every 1 to 3 months during cooling season. Homes with pets or high dust may need monthly changes.
3. Check the breaker and the outdoor disconnect
Find your electrical panel and look for the AC or condenser breaker. If it has tripped, switch it fully off and then back on. Also check the outdoor disconnect box near the condenser unit; it has a pull-out switch that can work loose.
If the breaker trips again immediately, stop and call a technician. Repeated tripping signals an electrical fault or a failing compressor.
4. Clear the outdoor condenser unit
The outdoor unit needs airflow on all sides. Clear away leaves, grass clippings, and mulch at least two feet around it, and gently rinse the coil fins with a garden hose from the inside out.
Never use a pressure washer on the fins; they bend easily. Straighten badly bent fins with a fin comb, available at any hardware store.
5. Look for a frozen evaporator coil
If you see ice on the copper refrigerant lines or the indoor coil, turn the system to FAN ONLY and let it thaw completely, which can take several hours. A frozen coil is usually caused by the dirty filter or low airflow you just fixed.
If the coil freezes again after thawing, the system may be low on refrigerant, which means there is a leak. Refrigerant work legally requires a certified technician.
6. Open vents and clear the condensate drain
Walk through the house and make sure supply vents are open and not blocked by furniture or rugs. Closing too many vents raises system pressure and reduces cooling.
Find the condensate drain line near the indoor unit. If the safety float switch has tripped, the system shuts off to prevent flooding. Clear the line with a wet vacuum or a cup of white vinegar, then reset the switch.
When to call an HVAC technician
Call a professional if the breaker keeps tripping, the coil refreezes, you hear grinding or screeching from the units, or the system is over 12 to 15 years old and struggling. Refrigerant leaks, compressor failures, and electrical faults are not DIY jobs. A certified technician can diagnose the real problem and tell you honestly whether repair or replacement makes more sense.