Short version: your AC freezes because the evaporator coil dropped below 32 degrees, and Florida’s wet air handed it plenty of moisture to turn into ice. The most common cause by far is restricted airflow, and the most common restriction is a dirty filter. Low refrigerant from a leak is second.
Do this first: set the thermostat to Off and the fan to On. That runs the blower with the compressor shut down and thaws the coil using room air. Give it several hours, do not chip at the ice, and do not run cooling while the coil is frozen. Then check the filter and replace it if light will not pass through.
If it freezes again after a new filter, something mechanical is wrong and it takes measurements to find.
The emergency procedure, step by step
- Thermostat to Off, fan to On.
- Wait three to six hours, up to a full day for a solid block. Put a pan under the air handler, since melting ice makes water fast.
- Do not chip at the ice. Coil fins are thin aluminum and puncture easily.
- Do not run the compressor while frozen. Ice blocks airflow, so liquid refrigerant returns to the compressor instead of vapor, and compressors cannot compress liquid.
- Replace the filter, open every register, clear furniture off returns.
- Restart and watch. If ice returns, call for service.
The physics, in plain English
Refrigerant boils inside the evaporator coil, and that boiling absorbs heat from your house. The temperature it boils at is set by the pressure in the coil, which depends on how much heat is arriving. Warm air across the coil is that heat source.
Take it away and pressure drops, so the boiling temperature drops too. Once the coil goes below 32 degrees, condensing moisture stops draining and starts freezing. Then it feeds itself: ice blocks airflow, which cuts heat, drops pressure, and makes more ice.
Why Central Florida makes it so much worse
A dry climate gives a coil mostly sensible load: lower the air temperature and you are done. Here you carry a heavy latent load on top, the energy needed to condense water vapor before air gets colder.
Orlando dew points sit in the low to mid 70s for months. A system in August pulls gallons of water a day out of your house and down the condensate drain. That water is why your coil sweats around the clock, and it is the raw material for ice.
So an airflow problem that would only run inefficiently in Phoenix becomes a frozen block here. Dirt sticks too, since a wet coil grabs dust and holds it.
The oversizing trap
Plenty of homes here run a system a half ton to a full ton larger than the house needs. Bigger is not better. An oversized unit hits setpoint fast and shuts off, and short cycles never keep the coil cold long enough to wring water out of the air. The house reads 74 and still feels clammy, so the owner sets it to 70, driving suction pressure lower and the coil toward freezing.
Long, steady cycles dehumidify a Florida house, which is why a properly sized AC installation starts with a load calculation, not square footage.
The seven real causes
- Dirty filter. Number one, and cheapest to fix.
- Closed or blocked vents. Registers shut in unused rooms, a couch against a return, a rug over a floor vent. All cut airflow.
- Dirty evaporator coil. Dust bonds to wet fins and forms a mat that insulates the metal and chokes the air path. Needs chemical cleaning.
- Undersized or leaky return duct. Common in older Orlando-area homes. Filter clean, equipment fine, but the return cannot deliver the air the blower wants.
- Low refrigerant from a leak. Less refrigerant means lower pressure and a lower boiling temperature. Systems do not consume refrigerant, so low charge means a leak.
- Blower problems. A weak motor, failing capacitor, dirt-packed wheel, or wrong speed tap. The fan sounds fine. It is not moving air.
- Cooling when it is cool outside. Below roughly 60 degrees, head pressure falls, suction pressure follows, and the coil can ice up even with a clean filter and good charge.
A clogged condensate drain is usually a companion rather than a root cause, but the two travel together: the slime that plugs the drain also coats the coil face. And when a frozen coil thaws, meltwater overwhelms a marginal drain, which is how this ends in a stained ceiling.
What a technician checks, and in what order
A good tech does not start with gauges and refrigerant.
- Look at the ice. Where it formed and how much narrows things fast.
- Read subcooling while it is still frozen. Low subcooling signals low charge.
- Inspect filter, blower wheel, coil face, and pan.
- Thaw completely. No measurement is accurate with ice on the coil.
- Measure airflow: static pressure across the air handler plus register readings. Target is roughly 350 to 400 CFM per ton. Most calls end here.
- Check blower amp draw, capacitor, speed tap.
- Recheck superheat, subcooling, and temperature split. In humid air the split reads lower than the textbook number, because much of the coil’s work removes water.
- Leak search if the charge is truly low, using an electronic detector and nitrogen test.
- Check the metering device and liquid line for a restriction if airflow and charge pass, then clear the drain and check the float switch.
DIY, prevention, and where the line is
Yours to handle. Check the filter monthly, not seasonally. Runtime drives loading and Florida systems run enormous hours, so a one-inch pleated filter often needs changing every 30 days in summer no matter what the box says. Keep two feet of clearance around the outdoor unit and rinse its coil gently, power off. Flush the drain line. Leave registers open.
Not yours. Refrigerant, blower motor, capacitor, metering device, coil cleaning, ducts.
Refrigerant is not a homeowner item, and that is not a sales pitch. EPA Section 608 restricts refrigerant sales and servicing to certified technicians. Topping off without finding the leak also means buying refrigerant that will be in your yard by next season. Airborne Tech Service holds Florida license CAC1822084 as a Certified Air Conditioning Contractor, and every refrigerant repair starts with finding the leak. See our AC repair in Central Florida page.
Get maintenance twice a year. Coil cleaning, drain treatment, capacitor testing, and airflow and charge verification catch every cause above before ice forms. That is the point of a preventative maintenance plan.
FAQ
How long does a frozen AC take to thaw?
Three to six hours with cooling off and the fan set to On. A heavily iced coil can take a full day. Running the blower alone speeds it up, because room air carries heat to the coil. Never chip the ice, since fins puncture easily.
Can I run my AC while the coil is frozen?
No. Ice blocks airflow, so liquid refrigerant travels back to the compressor instead of vapor. Compressors compress gas, not liquid, and slugging can destroy one in minutes. Shut cooling off, run the fan, and let the coil thaw fully before restarting.
Does a frozen coil always mean low refrigerant?
No. Restricted airflow causes more frozen coils than refrigerant does, and a dirty filter is the most common culprit. Low charge from a leak ranks second. A technician tells them apart by measuring subcooling, superheat, and airflow, not by guessing from symptoms.
Why does my AC freeze up in Florida more than it did up north?
Central Florida dew points sit in the 70s, so your coil stays wet and carries a heavy moisture load. That wet surface traps dirt and supplies endless water for ice. Systems also run far more hours per year, loading filters and coils quickly.
Is water leaking from my air handler related to the freezing?
Usually. When a frozen coil thaws, all that ice becomes water at once and can overrun the drain pan and line. A clogged, algae-filled drain makes the flooding worse and trips the float switch. Both should be fixed in one visit.
Can I add refrigerant myself to fix it?
No. EPA Section 608 restricts refrigerant sales and handling to certified technicians. Adding refrigerant also treats a symptom instead of the leak causing it. A licensed contractor finds the leak, repairs it, evacuates the system, and weighs in the correct charge.
Get it handled
A coil that freezes once will freeze again until the cause is fixed, and every cycle risks the compressor.
Airborne Tech Service is a family owned HVAC and commercial refrigeration company serving Orlando, Winter Park, Maitland, Altamonte Springs, Casselberry, Winter Springs, Longwood, Oviedo, Lake Mary, Sanford, Apopka, Kissimmee, and Deltona. Same-day availability, 24/7 emergency service, licensed under CAC1822084.
Call (321) 240-9346 or schedule service online. See our AC service in Orlando.