When your air conditioner runs but the house won't cool down, the cause is often something simple you can check yourself in a few minutes. Before you schedule a repair, try these five quick fixes. If none of them solves it, the section at the end explains when it's time to call a technician.
1. Check your thermostat settings
Start with the thermostat. Make sure it's set to Cool (not Heat, Off or Fan) and that the temperature is set a few degrees below the current room temperature. If the fan is set to On instead of Auto, the blower runs constantly and can push uncooled air between cycles, so switch it to Auto. If the display is blank or dim, replace the batteries. On a smart thermostat, check that a schedule, eco mode or away mode isn't overriding your setting.
2. Clean or replace your air filter
A dirty or clogged filter restricts airflow, which makes the AC struggle and can even freeze the indoor coil. Pull the filter and hold it up to a light; if you can't see light through it, replace it. Disposable filters should be replaced, not cleaned. Most homes need a new filter every one to three months, more often with pets or dust. If you see ice on the refrigerant lines or indoor coil, turn the system off and let it thaw for a few hours before running it again.
3. Inspect and clear the outdoor unit
The outdoor unit (condenser) releases the heat removed from your home. If it's dirty or blocked, it can't do that job and the air inside stays warm. To fix it:
- Turn the AC off at the thermostat and switch off the outdoor disconnect.
- Remove leaves, grass clippings, dirt and anything stacked against the unit.
- Gently rinse the coil with a garden hose from the inside out. Don't use a pressure washer, which can bend the fins. Near the coast, salt and sand buildup is common.
- Keep at least two feet of clear space around the unit.
Then check that the outdoor fan spins and the unit hums when the AC is calling for cooling. If the fan doesn't turn, the capacitor or fan motor may have failed and needs a technician.
4. Check the circuit breaker
Most central AC systems have two breakers in the electrical panel: one for the indoor unit and one for the outdoor unit. If either is tripped, the system may run partly or not at all. Switch a tripped breaker fully off and then back on. If it trips again, leave it off and call a technician; repeated tripping usually means an electrical problem or a failing compressor, and resetting it over and over can cause damage.
5. Clean the evaporator coil and check the drain
Over time the indoor evaporator coil collects dust that reduces its cooling capacity. If you can reach the coil access panel on your indoor unit:
- Turn the system off at the thermostat and the breaker.
- Remove the access panel and gently clean the coil with a soft brush or a no-rinse coil cleaner.
- Be careful not to bend the delicate fins or tubing.
While you're there, check the condensate drain pan. If it's full of water, the drain line may be clogged, and many systems have a safety switch that shuts the AC off until it's cleared. For a closer look at coil cleaning, see Can you use vinegar to clean AC coils?
When to call a professional
If you've worked through all five steps and your AC still isn't cooling, the problem is likely something that needs a licensed technician:
- Low refrigerant: this means there's a leak. It has to be found and repaired, not just topped off.
- A failed capacitor or contactor: common in the first hot weeks of summer.
- Compressor or fan motor problems
- Ductwork leaks or disconnections in the attic
- A system that's the wrong size for the home
Not sure what to check next? Our guide What should you check when your AC is not cooling? walks through the main components. To keep it from happening again, a yearly tune-up catches most of these problems early; see our maintenance plans.
AC repair across coastal North County and San Diego County
Precision Air Inc is a family-owned, licensed HVAC contractor (CSLB #996275). We repair and maintain all major brands of air conditioners, heat pumps and ductless systems, and we install high-efficiency Carrier, Bryant and Mitsubishi equipment. Learn more about our air conditioning services or request service.
Need service? Call (760) 858-8000, Monday–Friday 8–5, or send us a message.