It's 3 p.m. in July, the AC has been running all day, and the house is still 80°F. In Jacksonville's heat and humidity, this is one of the most common calls we get. The good news: the cause is often simple. Here are the 8 usual suspects, starting with the ones you can check yourself.
1. Thermostat settings or dead batteries
Make sure the thermostat is set to COOL, the temperature is below the room temperature, and the fan is set to AUTO. If the screen is blank or dim, replace the batteries. It sounds basic, but it's worth 30 seconds before anything else.
2. A dirty air filter
A clogged filter chokes airflow, so less cool air reaches your rooms. In Jacksonville's pollen season, filters fill up fast. Check yours and replace it if it looks gray. Most homes need a new filter every 1–3 months.
3. A frozen evaporator coil
If you see ice on the copper line near the outdoor unit or on the indoor unit, the coil has frozen. This is usually caused by poor airflow (a dirty filter or blocked vents) or low refrigerant. Turn the system to OFF and set the fan to ON for a few hours to let it thaw, then replace the filter. If it freezes again, call a technician.
4. A clogged condensate drain line
Florida humidity means your AC pulls gallons of water out of the air every day. That water drains through a small pipe that algae loves to clog. Many systems have a safety float switch that shuts the AC off when the drain backs up. Signs include water around the indoor unit, a full drain pan, or an AC that keeps turning itself off. A technician can clear and treat the line quickly.
5. A dirty or blocked outdoor unit
The outdoor unit (condenser) releases the heat from your home. If its coil is covered in dirt, grass clippings or pollen, or if bushes are growing against it, it can't get rid of heat, and cooling drops. Keep about 2 feet of space around it and gently rinse the coil with a garden hose (never a pressure washer). Near the beaches, salt air also corrodes these coils over time.
Tried the basics and still warm?
Our technicians are available 24/7 across Jacksonville. $89 diagnostic, upfront pricing.
6. Low refrigerant (a leak)
Your AC doesn't "use up" refrigerant. If it's low, there's a leak. Signs include warm air from the vents, a hissing or bubbling sound, ice on the lines and higher electric bills. A technician needs to find and repair the leak, then recharge the system to the manufacturer's spec. Older Jacksonville homes with original coils are especially prone to small leaks.
7. A failed capacitor or outdoor fan motor
If the outdoor unit hums but the fan doesn't spin, or the fan is spinning but the unit isn't blowing warm air out the top, an electrical part has probably failed. Capacitors often fail in extreme heat. This is a quick, relatively inexpensive repair, but the parts store a lot of electricity, so leave it to a professional.
8. Leaky ducts in the attic
Many Jacksonville homes run their ductwork through an attic that can reach 130°F or more in summer. If ducts are torn, disconnected or poorly sealed, you're cooling the attic instead of your living room. Rooms far from the air handler that never cool down are a common sign.
Why humidity makes everything feel worse
An AC does two jobs: it lowers the temperature and it removes moisture. If humidity stays high, 76°F can feel sticky and warm. An oversized system that runs in short bursts, a fan left on ON, or a dirty coil can all leave your home cool but clammy. Indoor humidity is most comfortable between 30% and 50%. If you can't get there, ask us about whole-home humidity control and air quality options.
Quick checklist before you call
- Thermostat on COOL, fan on AUTO, fresh batteries.
- Check the breakers for the indoor and outdoor units.
- Replace the air filter.
- Look for ice on the lines. If you see any, turn the system off and let it thaw.
- Make sure the outdoor unit is clear and its fan is spinning.
- Look for water around the indoor unit or drain pan.
Call a technician right away if you smell burning, the breaker keeps tripping, you hear grinding or screeching, the coil keeps freezing, or water is leaking into your home.
Frequently asked questions
How much cooler should the air from my vents be?
A healthy system usually blows air about 15–20°F cooler than the air going into the return vent. If the difference is much smaller, the system needs attention.
Should I set my thermostat fan to ON or AUTO in Florida?
AUTO is usually better in a humid climate. With the fan set to ON, it keeps blowing after cooling stops and can push moisture from the wet coil back into your home.
Why does my house feel cold but clammy?
That usually means the AC is lowering the temperature but not removing enough moisture. Common causes are an oversized system that runs in short bursts, a fan set to ON, or a dirty coil. Indoor humidity should ideally stay between 30% and 50%.
Can I add refrigerant myself?
No. Refrigerant work requires an EPA-certified technician, and low refrigerant means there is a leak. Adding more without fixing the leak only delays the problem.
We'll get your home cool again
24/7 AC repair in Jacksonville, Orange Park, Ponte Vedra and nearby communities.
Learn more about our AC repair service, or read how much AC repair costs in Jacksonville.
