Why Is My AC Frozen? Ice on the Coil or Lines in a Florida Home

What a frozen AC looks like

When airflow or refrigerant goes wrong, the indoor coil can drop below freezing. Moisture from humid Space Coast air then turns to ice instead of draining away.

Common signs:

• Frost or ice on the large insulated copper line at the outdoor unit
• Ice on the indoor coil or around the air handler in the closet, garage or attic
• Weak airflow from the vents, or air that isn't cold
• The system runs and runs but the house doesn't cool down

Ice feeds itself. The U.S. Department of Energy (DOE) says ice on the indoor coil "reduces airflow" and "can shorten compressor life" (DOE Building America Measure Guideline). Act early.

The two most common causes

1. Not enough airflow

The indoor coil needs a steady stream of warm house air across it. Without it, the coil gets too cold. DOE's guideline says very low airflow "can lead to system failure due to icing of the indoor coil and can shorten equipment life." It also notes that a fouled (dirty) evaporator coil "reduces airflow, will eventually cause the coil to freeze over, and may damage the compressor" (DOE Building America Measure Guideline).

Things that choke airflow:

• A dirty filter. This is the first thing to check. DOE says a clogged filter "restricts airflow through the unit" (DOE Energy Saver 101: Home Cooling). ENERGY STAR adds that a dirty filter "can increase energy costs and damage your equipment, leading to early failure" (ENERGY STAR Maintenance Checklist).
• Closed or blocked vents and returns, including furniture or rugs over a return grille.
• A dirty indoor coil, often from skipped filter changes.
• Duct problems. Crushed, disconnected or undersized ducts. DOE lists clogged or constricted ducts among common AC problems (DOE Energy Saver 101). See our ductwork page.
• A blower problem. That's a job for a technician.

2. Low refrigerant (which means a leak)

Refrigerant isn't used up like fuel. If a system is low, DOE says either it was undercharged at installation or it leaks, and "simply adding refrigerant is not a solution." A trained technician should fix the leak, test the repair, and then charge the system to the manufacturer's specification (DOE: Common Air Conditioner Problems, via Energy Saver 101). DOE's guideline explains that too little charge lowers the refrigerant's temperature in the coil, which "can lead to ice formation on the evaporator."

If your system is older and uses R-22, a leak raises bigger questions. See R-22 Phase-Out: What It Means If Your System Is Older and Repair or Replace Your AC in Brevard County?.

DOE's guideline also lists refrigerant line restrictions and a faulty expansion valve. Those need gauges and training to diagnose.

What to do right now

1. Turn the system to Off at the thermostat. Running a frozen system keeps building ice and strains the compressor.
2. Set the fan to On if you'd like the ice to melt faster. This moves warm house air across the coil. Switch the fan back to Auto once you're running normally again (see our thermostat guide for why Auto matters in Florida).
3. Check the filter. If it's dirty, replace it with the size printed on the old filter's frame.
4. Open vents and clear returns.
5. Watch for water. Melting ice can overflow the drain pan. If water is spreading or near anything electrical, leave the system off and call.
6. Let the ice melt completely before turning cooling back on.

Don't:

• Chip, scrape or pry at the ice. Coil fins and copper lines damage easily.
• Add refrigerant yourself. Refrigerant work belongs with a technician certified under EPA's Section 608 program (EPA Section 608).
• Open electrical panels on the indoor or outdoor unit.

Not sure what you're looking at? Ask Mikey. Mikey is free, walks you through safe checks, and hands you to a real person when it's time.

When to call

Call for AC repair if:

• The ice comes back after you've changed the filter and let it thaw
• Your filter was clean and the vents were open, but it froze anyway
• Water has leaked into ceilings, floors or walls
• The system is older and has needed refrigerant before

A technician checks airflow, the blower, the coil, the drain and the refrigerant charge. If refrigerant is low, the leak gets fixed before the system is charged.

How to keep it from happening again

• Check the filter monthly and replace it every 1 to 3 months.
• Keep returns and vents clear.
• Get regular professional maintenance. ENERGY STAR recommends having coils cleaned, because dirty coils reduce the system's ability to cool your home (ENERGY STAR). See our HVAC maintenance service and the Space Coast AC Maintenance Checklist.

Small businesses

Shops and offices freeze up for the same reasons, and busy or dusty spaces may need more frequent filter changes. See light commercial.

The next step

A frozen AC is a symptom, not the problem. We find the cause, fix it properly, and quote in writing. We serve homes across Brevard County, including Melbourne, Palm Bay, Titusville, Cocoa, Merritt Island and Viera.

• Start My Estimate
• Ask Mikey (Mikey is free)
• Call (321) 405-1806

Firefighters, law enforcement, EMS and paramedics, healthcare workers, teachers, ministry, government employees and military (active and veterans) can get 10% off the total, up to $2,500, on new units and repairs through our Local Heroes program. Family members of eligible heroes qualify too. It can't be combined with other offers.

Frequently asked questions

Sources

1. DOE Building America Measure Guideline
2. DOE Energy Saver 101: Home Cooling
3. ENERGY STAR Maintenance Checklist
4. EPA Section 608

Written by Cooling 321, Space Coast, Brevard County, FL. State Certified Air Conditioning Contractor, License No. CAC1825377. General information only; your system and home are reviewed before any recommendation.