Troubleshooting · Water and ice

AC Frozen Up? Why There's Ice on the Coil or Lines and How to Fix It

Ice on the copper lines or indoor coil, weak airflow, water as it melts.

By Mark Curant·Updated October 14, 2026

Most likely causes

A clogged filter or blocked return vents restricting airflow
Closed or blocked supply vents
Low refrigerant from a leak
A dirty indoor (evaporator) coil
A weak or failing blower motor
Running the AC on cool nights (below about 60°F outside)

Before you open anything

Turn the system off at the thermostat, then switch off power at the breaker and at the disconnect beside the outdoor unit. Never touch the capacitor, even with the power off: it can hold a dangerous charge. Refrigerant work is for licensed technicians only. Reset a tripped breaker once; if it trips again, leave it off.

Don't use a hair dryer or heat gun on the coil, and never try to add refrigerant yourself. Newer systems use mildly flammable refrigerants (R-454B, R-32), and handling refrigerant requires EPA certification.

Check these first (free, 5 minutes)

Turn cooling off now. Running a frozen coil can send liquid refrigerant back to the compressor and damage it.
Air filter: replace it if it's dirty.
Vents: open supply registers and clear furniture or curtains away from return grilles.
Indoor fan: is air coming out of the vents at all when the fan runs?

Causes, signs and repair costs

Clogged filter or blocked returns

DIY

Weak airflow everywhere, filter gray

Typical cost: $5–$20

Closed supply vents

DIY

Several rooms with vents shut; often done to "save energy"

Typical cost: $0

Low refrigerant (a leak)

Pro

Freezing keeps coming back with a clean filter; cooling has gotten worse over time

Typical cost: $400–$2,400 to find, fix and recharge

Dirty indoor coil

Pro

Old system, filters often skipped; dust matted on the coil

Typical cost: $75–$200 service call plus cleaning

Weak or failing blower motor

Pro

Fan sounds slow or laboring; airflow weak with a clean filter

Typical cost: $500–$1,200

Running in cool weather

DIY

Freezes on mild nights, fine on hot days

Typical cost: $0

Cause	Signs	Who fixes it	Typical cost
Clogged filter or blocked returns	Weak airflow everywhere, filter gray	DIY	$5–$20
Closed supply vents	Several rooms with vents shut; often done to "save energy"	DIY	$0
Low refrigerant (a leak)	Freezing keeps coming back with a clean filter; cooling has gotten worse over time	Pro	$400–$2,400 to find, fix and recharge
Dirty indoor coil	Old system, filters often skipped; dust matted on the coil	Pro	$75–$200 service call plus cleaning
Weak or failing blower motor	Fan sounds slow or laboring; airflow weak with a clean filter	Pro	$500–$1,200
Running in cool weather	Freezes on mild nights, fine on hot days	DIY	$0

Typical U.S. installed prices in 2026. Most repairs also carry a service call fee of $75–$200, often credited toward the repair. See AC repair costs in 2026 for the full list.

Step by step

1
Switch cooling off and the fan on
Set the thermostat to Off and the fan to On. Blowing room air across the coil thaws it much faster than leaving everything off. Expect a few hours, longer for heavy ice. Don't chip or scrape the ice; the coil fins and tubes are easily damaged.
2
Protect against the melt water
A lot of water comes off a thawing coil at once. Put towels around the indoor unit and check that the drain pan isn't overflowing.
3
Fix the airflow
Fit a new filter, open all supply vents and clear the return grilles. These are the most common causes, and the only ones you can fix yourself.
4
Restart and watch
When the coil and lines are completely clear and dry, switch back to Cool. Check the large copper line at the outdoor unit after an hour: cold and sweating is normal, frost or ice is not.

Call a technician if

Ice comes back within a day or two after thawing with a clean filter and open vents
Airflow from the vents is weak even with a new filter
You hear hissing or see oily spots on the lines (signs of a leak)

Red flags on a quote

A refrigerant recharge with no leak search or repair: it will freeze again
A new coil quoted before anyone has checked airflow and the refrigerant charge

Facing an expensive repair on an older system? Run it through the repair vs replace calculator, or read the $5,000 rule.

Frequently asked questions

Why is my AC freezing up?

An evaporator coil freezes when it gets too cold, which happens when too little warm air passes over it (a dirty filter, blocked vents, a failing blower) or when there's too little refrigerant. Airflow problems are the most common and the easiest to fix.

How long does it take for a frozen AC to thaw?

Usually a few hours with the fan on and cooling off, and up to a day for heavy ice. Don't restart cooling until the coil and copper lines are completely clear.

Can I run my AC while it's frozen?

No. A frozen coil cools almost nothing, and running it can push liquid refrigerant back to the compressor, which can damage it. Turn cooling off and run the fan until the ice is gone.