What’s Happening

A frozen A/C coil almost always means one of two things: airflow to the coil has been cut off, or refrigerant is running low. Either way, your system cannot cool your home while the coil is encased in ice, and running it in this condition risks burning out the compressor – a significantly more expensive repair than whatever caused the freeze in the first place.

Call (817) 402-2972

Here’s the plain version of what’s going on. Your evaporator coil is the part inside your air handler that absorbs heat from the air in your home. It does that job by staying cold – very cold – but it needs a steady stream of warm air moving across it to keep the temperature above the freezing point of moisture. When that airflow drops, or when refrigerant pressure falls, the coil surface drops below 32°F, moisture in the air freezes onto it, and you end up with a block of ice where a coil should be. The system stops cooling, water starts dripping as the ice melts, and you’re standing here reading this.

Why It Happens

Clogged or Collapsed Air Filter

This is the most common cause by a wide margin. A dirty filter chokes off the airflow the evaporator coil needs to stay above freezing. Pull your filter right now. If it looks gray, matted, or feels like a solid pad of dust, restricted airflow is almost certainly the culprit. Filters that have been in place for three months or more are suspects even if they look passable from the outside.

Low Refrigerant (a Leak, Not Evaporation)

Refrigerant does not get “used up” in a healthy system – if the level is low, there is a leak somewhere. Low refrigerant causes pressure inside the coil to drop, which drives the coil temperature below freezing. You can’t see the leak itself, but signs that point to this cause include ice forming even after you’ve changed the filter, a hissing or bubbling sound near the indoor unit, or a system that blows cool but not cold air for weeks before the freeze-up.

Blocked or Closed Supply Vents

Closing off vents in unused rooms feels sensible but actually disrupts the system’s airflow balance. Walk through your home and check that every supply register is open and unobstructed – furniture, rugs, and drapes pushed against vents are frequent offenders. If several vents are blocked or closed, that alone can drop airflow enough to freeze the coil, particularly in smaller systems or older ductwork.

Failing Blower Motor or Fan

The blower motor is the fan that pushes air across the evaporator coil. When it starts to fail, airflow drops – same result as a clogged filter, but with a different fix. Listen for unusual sounds from the air handler: a humming that seems labored, intermittent operation where the fan kicks on and off when it shouldn’t, or air that feels weak at the registers even with the thermostat set low. A struggling blower is a mechanical problem a technician needs to diagnose.

What to Do Right Now

• Turn the system to “Fan Only” or switch it off at the thermostat. Do not keep running it in cool mode. Ice on the coil will not melt until heat can reach it, and running the compressor against a frozen coil puts serious strain on it. Give the coil two to four hours to thaw on its own, or longer if the freeze is heavy.
• Check and replace your air filter. Find the filter slot on your air handler or return air grille, pull the filter out, and hold it up to a light source. If light barely passes through, replace it before you call anyone. This step alone occasionally resolves the freeze after a full thaw cycle – though if it recurs, something deeper is wrong.
• Photograph what you’re seeing before it thaws. Ice coverage, water dripping location, anything unusual – a photo on your phone takes seconds and gives the technician useful information even if the ice is gone by the time they arrive.
• Place towels around the base of the air handler. A heavily iced coil can release a surprising amount of water as it thaws. Getting a towel under the unit now prevents water damage to flooring or the ceiling below if the unit is in an attic.
• Do not attempt to chip or scrape the ice off the coil. The evaporator coil fins are thin aluminum and bend easily. Damaging them reduces airflow permanently and can make a manageable repair significantly worse. Let the ice melt on its own.

How We Fix It

When your local Coldharbour Heating & Air technician arrives, the first thing they do is a full visual inspection – the coil, the filter housing, the blower assembly, and the refrigerant lines. If the system was running in cool mode right up until you called, they may let it continue thawing for a short period before they can get a clear look at the coil surface.

From there, the diagnostic path follows the evidence. If airflow was the cause, the technician checks the blower motor speed and condition, inspects the ductwork for obvious collapse or disconnection, and confirms the filter housing is sealing properly. If refrigerant is the likely cause, they attach manifold gauges to measure system pressures and locate the source of the leak before any refrigerant is added – adding refrigerant without fixing the leak is a short-term patch, not a repair.

Most frozen-coil calls resolve the same day through our AC repair service. The written price is in your hand before any work starts – that is not optional, it is how every Coldharbour job works under The Kingswell Way. The repair is covered by the 365-Day Done Right Promise: if it fails within a year, we come back and correct it at no charge. That is in writing before the technician leaves your door.

Frequently Asked Questions

Get It Fixed

Your local Coldharbour Heating & Air team is ready to diagnose and repair your frozen coil today. A live person is on the phone right now – call (817) 402-2972 or book online. You’ll have a written price before any work begins, and the repair comes with our 365-Day Done Right Promise.

Written by Victor Mancini, Owner and Lead HVAC Technician at Coldharbour Heating & Air, proudly serving communities as part of the Kingswell network since 2003.