AC Freezing Up in Florida
Ice on the coil or the copper line? Liberty Air and Electric finds what caused it and fixes that.
- The filter check is free
- Cooling off, fan on, thaws it in hours
- Diagnostic once the ice is gone
What Makes an AC Freeze Up in Florida
Liberty Air and Electric works a freeze-up from the cheapest cause up, because the first two cost the price of a filter and the rest need gauges or a multimeter.
If you are reading this you have probably already found the ice, on the indoor coil or on the copper line running out to the condenser. The system will keep running that way until somebody stops it, and running it frozen is the part that does damage.
Ice means one of two things. Either not enough warm air is getting to the evaporator coil, or there isn't enough refrigerant in it. The filter is what you can rule out for free, so start there.
The filter is grey and stiff
Pull it out and hold it up to a light. If almost nothing comes through, that is your answer and it costs the price of a filter. A starved coil runs colder and colder until the moisture on it turns to ice.
You can fix thisYou recently upgraded to a higher-MERV filter
A jump from a basic filter to a high-MERV one is the cause people never suspect, because it felt like an upgrade. The filter can be spotless and still be too restrictive for the equipment behind it.
You can fix thisIce, the outdoor unit running, and no air at the vents
Stand at a supply register with the system on. If you can hear the unit running outside and feel nothing at the vent, the indoor blower has quit moving air. Call before it runs any longer.
Call a proIce with a filter you just changed
A clean filter, a blower that is still moving air, and ice anyway. That combination points at the refrigerant charge. Refrigerant is not consumed, so a system running low has a hole somewhere.
Call a proAirflow feels weaker at the vents
Air that feels weak at the registers, or a room that never keeps up, can mean a supply main has collapsed somewhere in the attic. Everything past the collapse gets less, and the airflow the coil needs goes with it.
Call a proIt thawed and has not frozen again
Good news, though nothing has been fixed yet. Unless the filter was the cause, whatever restricted the system is still there and the next freeze is on its way.
Call a pro anywayLiberty Air and Electric would rather you check the filter first
- A filter costs less than a service call
- Diagnostic fee waived with an approved repair
- Upfront pricing before any work starts
What to Do the Moment You See Ice on the AC
Liberty techs give every caller with a frozen system the same two instructions first. Cooling off. Fan on.
Set the thermostat cooling to off and the fan to on rather than auto. That pushes room air across the frozen coil and cuts the thaw down to a few hours. Two reasons to do it now.
First is the compressor. Running a frozen system sends liquid refrigerant back to a pump built for vapor, and that's how a few hundred dollars of airflow work turns into AC compressor repair.
Second is scheduling, and telling you this costs us a same-day ticket. Nobody can measure anything through a block of ice, so a truck that shows up while the coil is solid just sits there and waits. Book the visit for later in the day or the next morning, and spend the time in between thawing it out.
Check the AC Filter Before You Call Anyone
A restricted filter costs nothing to rule out, and it's the first thing to check on a Florida system that ices up. Pull the filter and hold it up to a light. If the light barely comes through, replace it and let the system thaw before you book anything. Plenty of freeze calls end right there.
A brand new filter can freeze a system too
If you normally run a basic filter, went out and bought a much higher-MERV one, and the system started freezing after that, the new filter is the likely reason. It's spotless, and the blower was never sized to pull air through it.
The rating tells you what the filter catches. It says nothing about what your blower can pull air through. The EPA recommends MERV 13 or as high as the system will accommodate, and that second half matters. In Florida the 1 inch filter is the most common size, and most systems can't handle a 1 inch MERV 13, especially 4 and 5 tons. Better filtration without choking the airflow means a deeper media cabinet with more surface area, which is what whole-home filtration in Florida gets into.
Put the old style of filter back in and see whether the freezing stops. That test costs one filter.
Filter was clean and it froze anyway?
Book a diagnostic. We measure the system, show you what we find, and quote the repair before any work starts.
Liberty Air and Electric splits what's left into three, and you can narrow it down before the truck gets there just by listening and standing at a vent.
The blower has quit, and this one is urgent
Stand at a supply register while the system is calling for cooling. If you can hear the outdoor unit running and there's no air at the vent, the indoor blower has stopped. Nothing is carrying heat to the coil, so it freezes fast and hard. That combination, ice plus a compressor you can hear plus nothing coming out of the vents, is the urgent one. Don't wait until tomorrow. The job itself sits under AC fan motor replacement.
A supply duct has collapsed rather than torn
Most duct trouble is a leak, a hole dumping cold air into the attic. A freeze-up is usually the opposite. A supply duct, usually a main line off the air handler, goes flat and blocks the air. The cold air stays in the cabinet, the coil ices over, and everything past the collapse gets nothing.
Flex duct makes it possible. A run that gets crushed, kinked over a truss, or sags far enough can close off without ever tearing. Ducts get sized against the ACCA Manual D standard our installers design to, and a collapsed main puts the system well under what that design counted on. Out in Wedgefield, where the ductwork runs through attics that hit 130 degrees by mid-afternoon, flex sags and sets in place over the years, which is why ductwork in Wedgefield shows up on a cooling call more often than a duct call. Reopening or replacing the run is duct repair and replacement work.
A refrigerant leak, and the ice is telling you something good
Ice with a clean filter and a working blower usually means the charge is low. Refrigerant doesn't get used up the way fuel does, so a system running low has a hole in it, and refrigerant leak detection is how we find it.
The ice is good news here. If the system is low enough to freeze, the leak is a small one. It takes real refrigerant still moving through that coil to drive it below freezing with moisture condensing on it. A big leak doesn't make ice at all. It just quits cooling. So the ice tells you most of the charge is still in there, and a smaller leak means the compressor has been working under less strain.
Liberty Air and Electric wants a number before anybody blames the metering device, including when one of our own techs is the one blaming it. The valve meters refrigerant into the evaporator coil, and when it fails it can freeze a system.
It also gets blamed a lot more often than it fails. The valve sits inside the cabinet where nobody can look at it, it's the last thing left after everything else checks out, and blaming it doesn't require measuring anything. A guess sounds exactly like a measurement when you're standing in your own driveway listening to it.
One question separates the two. Ask what the superheat measured. Superheat is the reading that says whether refrigerant is metering right, so it has to be out of range before the valve is the answer at all. A technician who diagnosed the valve has that number and will give it to you. A technician who never mentions superheat almost certainly got there by elimination.
You don't need to know what a good superheat number looks like. Asking the question is the whole test.
The AC Thawed and Has Not Frozen Again
A system that thaws and then runs fine for a few days looks like a problem that fixed itself. With one exception, it didn't.
If the filter was the cause and you replaced it, that's a real fix and you're done. Otherwise the restriction or the leak is still there and the system just hasn't iced up again yet. Overnight is usually when it does, because the cooling load drops after dark and a system already short on airflow or charge freezes. Get a technician out in the next few days. Waiting for the second freeze usually means it lands on the hottest afternoon of the week.
How Liberty Handles a Frozen AC Call
Liberty Air and Electric books a frozen system for after it's thawed, because showing up early just means sitting in the driveway. Once the coil is clear, the work is measuring. Airflow across the coil, static pressure across the filter and the ducts, the charge, and the superheat and subcooling that tell us whether refrigerant is metering right.
Those readings sort the causes out in one visit. Low airflow with a normal charge points at the filter, the blower, or the ducts. A normal blower with a low charge points at a leak. Correct airflow and a correct charge with superheat out of range is what a real metering-device failure looks like, and that's the only time that diagnosis is worth paying for.
A coil that froze because it was filthy is its own case, and evaporator coil cleaning handles that one. Liberty covers Greater Orlando and South Florida, and freeze-ups run heaviest here from June through September, when the humidity gives a restricted coil plenty of water to freeze.
Questions?
Frequently Asked Questions About an AC Freezing Up
Q: Why is my AC freezing up?
A: An AC freezes up when something stops enough warm air from reaching the evaporator coil, or when the refrigerant charge is low. A clogged filter, a filter that is too restrictive, a blower that has quit, a collapsed supply duct, a dirty coil, and a refrigerant leak all produce the same block of ice.
Q: How long does it take for a frozen AC to unfreeze?
A: A frozen AC takes roughly two to eight hours to unfreeze with the cooling switched off and the fan left on. A coil buried in a solid block of ice, especially in an attic air handler, can take most of a day. Running the fan alone moves room air across the coil and cuts that time down considerably.
Q: Should I keep running my AC if it is frozen?
A: Do not keep running an AC that is frozen. A frozen system sends liquid refrigerant back toward the compressor instead of vapor, and a compressor is built to pump vapor. That turns a repair worth a few hundred dollars into one worth a few thousand. Set cooling to off and the fan to on.
Q: Can a dirty air filter make an AC freeze up?
A: A dirty air filter makes an AC freeze up regularly, and it is one of the two causes a homeowner can fix without a technician. The filter starves the evaporator coil of the warm air it needs to absorb heat, so the coil keeps dropping until the condensation on it turns to ice.
Q: Can a MERV 13 filter make my AC freeze?
A: A MERV 13 filter can make an AC freeze if the system was not designed for that much resistance. Filtration ratings describe what a filter catches, not what your equipment can pull air through. A one-inch high-MERV filter dropped into a system built around a basic one restricts airflow enough to ice a coil.
Q: Why does my AC freeze up at night?
A: An AC freezes up at night because the cooling load falls after dark while the system keeps running. Lower outdoor temperatures and a quieter house mean less heat reaching the coil, so a system already marginal on airflow or charge crosses the freezing line overnight and looks fine by afternoon.
Q: Does a frozen AC always mean a refrigerant leak?
A: A frozen AC does not always mean a refrigerant leak, though a leak is one of the common causes. Airflow is the other side of it: a clogged filter, a restrictive filter, a failed blower, a dirty evaporator coil, or a collapsed duct. A technician separates the two by measuring airflow and charge, because the ice itself looks the same either way.
Q: Is a bad metering device a common cause of a frozen AC?
A: A bad metering device is a genuine cause of a frozen AC but a less common one than airflow or refrigerant problems. It also gets blamed more often than it fails, because it is what a technician reaches for after ruling other things out. Ask what the superheat measured before accepting that diagnosis.
Q: Can a frozen AC damage the compressor?
A: A frozen AC damages the compressor when it is left running. Liquid refrigerant that fails to boil off in an iced coil travels back down the suction line to a compressor designed to handle vapor only. Shutting the cooling off at the first sign of ice is what prevents that.