Why Is My AC Not Cooling? 9 Causes and Fixes for Sarasota Homes
Your AC is running but the house keeps getting warmer. This guide walks through why an AC not cooling is usually one of nine problems, which ones you can check safely in five minutes, and which need a professional technician.
Quick answer
An AC that runs but won’t cool usually has one of four problems: the thermostat is set wrong, the air filter is clogged, the indoor coil has frozen, or the outdoor unit has stopped, often from a failed capacitor. Check the thermostat and filter yourself. If you see ice on the copper lines or the outdoor fan isn’t spinning, switch the system off and call a technician.
Key takeaways
- Start with the thermostat (set to Cool and Auto) and the filter. Those two fix a surprising number of calls.
- Ice on the lines means low airflow or low refrigerant. Turn the system off and let it thaw before anything else.
- If the indoor fan runs but the outdoor unit is silent or just hums, switch it off. Running it can damage the compressor.
- A healthy system cools the air about 15 to 20 degrees between the return and the supply vents.
- Topping up refrigerant without fixing the leak only buys a few weeks.
AC Not Cooling Well? The Common Causes and Who Can Fix Them
These are the nine faults behind most AC not cooling calls in Sarasota. The right column tells you whether it is safe to check yourself.
| Cause | Signs | Fix |
|---|---|---|
| 1. Thermostat settings | Set to Heat or Fan On, schedule overriding you, dead batteries | Check yourself |
| 2. Clogged air filter | Weak airflow, dust around vents, filter grey and solid | Check yourself |
| 3. Tripped breaker or switch | Outdoor unit completely silent | Reset once |
| 4. Blocked drain, float switch tripped | Water in the pan, system shuts off on its own | Check, then call |
| 5. Frozen evaporator coil | Ice on copper lines, little air from vents | Thaw, then call |
| 6. Failed capacitor or contactor | Outdoor unit hums or clicks, fan doesn’t spin | Technician |
| 7. Refrigerant leak | Runs all day, air only slightly cool, ice, hissing | Technician |
| 8. Dirty or corroded outdoor coil | Struggles on hot afternoons, worse near the coast | Technician |
| 9. Leaky ducts or wrong size system | Some rooms never cool, house feels damp | Technician |
ENERGY STAR notes that airflow problems alone can cut a system’s efficiency by up to 15 percent, and dirty coils make the system run longer to do the same job. In a Sarasota summer, that is often the difference between a house that holds 75 degrees and one that drifts to 82.
Check These Things Before You Call
Work down this list in order. Each step takes a minute or two and none of them needs tools.
AC not cooling: a five minute check
Stop at the first step that finds the problem.
- Is the thermostat set to Cool, on Auto, and below room temperature?
Yes Go to step 2.
No Fix the setting, wait 15 minutes. - Is the air filter clean enough to see light through?
Yes Go to step 3.
No Replace it. A clogged filter can freeze the coil. - Is there ice on the copper lines or the indoor unit?
No Go to step 4.
Yes Turn the system off and let it thaw. See the frozen coil section below. - Is the outdoor unit running, with the fan spinning?
Yes Go to step 5.
No Check the breaker once. If it hums but won’t start, switch off and call. - Is there water in the drain pan under the indoor unit?
No Go to step 6.
Yes The drain is blocked and the float switch may have shut things down. Call to clear it. - Is the air from the vents at least 15 degrees colder than the air going into the return?
Yes The AC is working. Look at ducts, sizing or humidity.
No Likely refrigerant, coil or airflow. Book a technician.
Why Is My AC Not Cooling but the Fan Is Running?
This usually means the indoor blower works but the cooling side doesn’t. Go outside and look at the condenser.
- Outdoor unit silent: check the breaker and the disconnect switch beside the unit. A tripped breaker that trips again when reset points to an electrical fault. Leave it off.
- Outdoor unit humming, fan not spinning: the classic failed capacitor. Summer heat wears them out, and lightning surges finish them off. Switch the system off so the compressor doesn’t overheat, then call. It is usually a quick fix.
- Everything running, air barely cool: low refrigerant from a leak, or a dirty outdoor coil that can’t shed heat. Both need a technician with gauges.
If this happens at night or on a weekend and the house is getting dangerously hot, our emergency AC repair line answers around the clock. Otherwise, a same day AC repair visit in Sarasota is usually all it takes.
Outdoor unit humming but not running?
Turn it off and get a free quote. Capacitor swaps are one of the most common same day fixes.
What to Do When Your AC Unit Freezes Up Inside
Ice on an air conditioner in Florida sounds strange, but it happens when too little warm air crosses the indoor coil, or when refrigerant is low. The coil drops below freezing and moisture from the air turns to ice.
Switch cooling off
Set the thermostat to Off so the compressor stops.
Run the fan
Set the fan to On. Moving room air over the coil thaws it faster.
Check the filter
Replace it if it’s dirty, and make sure supply vents and returns aren’t blocked by furniture.
Watch the drain pan
Thawing ice makes a lot of water. Keep towels nearby.
Restart after it's clear
Usually a few hours. If it freezes again within a day, the cause is airflow or refrigerant and needs a technician.
Don’t chip the ice off. The coil fins bend easily and a nicked line can leak. Let it melt on its own.
How to Reset an AC Unit Safely
A reset can clear a system that tripped after a power cut or a lightning storm. Do it once, not repeatedly.
- Set the thermostat to Off.
- Switch off the AC breaker in your electrical panel and the disconnect beside the outdoor unit.
- Wait at least five minutes so pressures settle.
- Switch both back on, then set the thermostat to Cool a few degrees below room temperature.
If the breaker trips again, or the system runs but still blows warm air, stop there. Repeated resets can damage the compressor, which is one of the most expensive parts to replace.
Is the AC Actually Cooling? Measure the Temperature Split
You can check this with any kitchen or digital thermometer. Hold it at a return grille for a minute, then at a supply vent near the indoor unit after the system has run for 15 minutes.
The temperature split test
76°F Air into the return | 58°F Air from a supply vent | 18°F Temperature split
- Under 15°F: not cooling properly
- 15 to 20°F: normal
- Over 22°F: possible airflow problem
A common industry rule of thumb, used here as an example. High humidity days can lower the split slightly. A technician measures it properly along with refrigerant pressures.
A good split but a warm house points away from the AC itself and toward leaking ducts, an undersized system or heat gain through windows. Leaky attic ducts are very common in older Sarasota homes. Our duct sealing service fixes those.
Why Sarasota Air Conditioners Struggle in August
- Long run hours. Systems here run most of the year, so parts wear out on hours, not age.
- Humidity. Your AC removes moisture as well as heat. A system that is too big cools fast and shuts off before the air dries out, so the house feels warm and sticky at 74 degrees.
- Design limits. Most homes are sized to hold around 75 degrees on a typical hot afternoon. Asking for 68 when it’s 95 outside will keep the system running nonstop without getting there.
- Salt air. On Siesta Key, Lido and Longboat Key, outdoor coils corrode years early. A gentle fresh water rinse every few months helps.
- Hot attics. Ducts in a 130 degree attic lose cooling fast if the joints have come apart.
If your house always feels clammy, read about humidity control in Sarasota. If the system is old and keeps failing, our guide to new AC unit costs shows what replacing it would really cost.
When to Call a Technician
Call straight away if any of these apply:
- Ice comes back after thawing
- The outdoor unit hums, buzzes or clicks but won't start
- The breaker trips again after one reset
- You hear hissing or bubbling from the lines
- You smell burning or hot plastic
- Water is coming through a ceiling
Refrigerant work requires an EPA Section 608 certified technician, so a leak is never a DIY job. We’ll find the fault, give you the price before any work, and fix most problems on the first visit. For heat pumps, see our heat pump repair page. We cover all of Sarasota plus Bradenton and Palmetto.
How to Stop It Happening Again
ENERGY STAR recommends a professional check of the cooling system every spring and checking your filter monthly. A tune-up cleans the coils, tests the capacitor before it fails, and flushes the drain line that causes so many Florida breakdowns. See what’s included in our AC maintenance visits in Sarasota.
AC Not Cooling Questions
Why is my AC blowing warm air?
Most often the outdoor unit has stopped while the indoor fan keeps running, usually from a failed capacitor or a tripped breaker. Low refrigerant and a thermostat set to Heat or Fan are the other common causes.
Why is my AC running but the house is still hot?
Check the filter and look for ice on the lines first. If both are fine, measure the temperature split. A normal split with a hot house points to leaky ducts, an undersized system or heat gain through windows rather than a broken AC.
How long should it take my AC to cool the house?
It depends on the house, the size of the system and how hot it got inside, so there’s no single number. A healthy system brings the temperature down steadily. If it runs for hours and the thermostat reading doesn’t move, something is wrong.
Can I just add refrigerant to my AC?
No. Refrigerant doesn’t get used up, so low refrigerant means a leak. Adding more without fixing it buys a few weeks at most, and handling refrigerant legally requires an EPA certified technician.
Is it bad to keep running an AC that isn't cooling?
Yes, if there’s ice or the outdoor unit is struggling. A frozen coil or a compressor that can’t start can turn a small repair into a big one. Turn it off and get it checked.
Why is my AC not cooling upstairs?
Heat rises, and upstairs rooms often sit under hot attics with long duct runs. Leaky or undersized ducts, closed vents and an oversized single zone system are the usual culprits. Zoning or a ductless mini split can help.
Written by The Sarasota AC Repair Pros team
Local HVAC contractor serving Sarasota and Manatee County. We wrote this guide around the questions Sarasota homeowners ask most and checked every figure against the published sources listed below. Last reviewed October 3, 2026.
On this page
- AC Not Cooling Well? The Common Causes and Who Can Fix Them
- Check These Things Before You Call
- Why Is My AC Not Cooling but the Fan Is Running?
- What to Do When Your AC Unit Freezes Up Inside
- How to Reset an AC Unit Safely
- Is the AC Actually Cooling? Measure the Temperature Split
- Why Sarasota Air Conditioners Struggle in August
- When to Call a Technician
- How to Stop It Happening Again
- Questions
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