Home AppliancesAir Conditioner

How To Tell if AC Coils Are Frozen

Frozen Air Conditioner Coils

When it’s cold outside, homeowners and renters often get concerned about their AC coils potentially freezing up.

Knowing the early signs of freezing AC coils can prevent you from needing to call out a contractor and going without clean air.


The common signs of frozen AC coils aren’t too difficult to notice. When you’re concerned about your AC in cold weather, check for these signs when your air conditioner is being operated:

  • Your AC is blowing warm air instead of cold air.
  • Decreasing your AC’s temperature doesn’t cool the air coming out of the machine.
  • Changing the setting from low to high makes no difference to the warm air being blown out.

Any signs of warm air coming out of an AC unit should be a warning to you. If the air is warm, your coils are more than likely going to be frozen.

As well as knowing the signs of frozen AC coils, it’s important to know what happens when coils freeze up and what you can do to fix the problem – preferably without paying someone else to come out and fix it for you.

3 Ways To Fix Frozen AC Coils

Ways To Fix Frozen Ac Coils

Now that you know the sign of frozen AC coils let’s look at how to fix them before your air conditioning unit becomes damaged.

1. Check Your Air Filter

Check Your Air Filter

A clogged air filter can make the AC unit cool and freeze up because of the restricted airflow.

Check that your air filter hasn’t been installed backward or blocked up with dirt and debris over time.

If it does look messy, change your air filter and see if that makes any difference.

2. Turn On Your AC’s Fan

Turn On Your Ac’s Fan

Before turning the fan on – which should push more air over the indoor coil and help to unfreeze it – be sure to turn off your AC’s thermostat.

This method may take a few hours because you’re pushing cool air over frozen equipment.

3. Activate Defrost Mode

Activate Defrost Mode

Not all AC units have this option, but yours might. Check your unit or manual for mention of a “defrost mode” and turn it on.

AC units with defrost modes have a built-in heat pump for times like this. The defrost mode will unfreeze your AC’s coils.

Additionally, your AC’s manual may have a de-icing guide.

Do Not Take Apart Your AC Unit

If you aren’t familiar with the inner workings of your model air conditioning unit, do not attempt to take it apart.

If your unit is insured, this will likely void the warranty.

As much as you may want to look at the coils yourself, you do not need to see them to fix a freezing issue on most AC units.

What Happens When Your AC Coil Freezes?

What Happens When Your Ac Coil Freezes?

A frozen AC coil is exactly what it sounds like. There’s usually a build-up of ice on the coils inside the AC unit, which prevents the unit from functioning correctly.

The coils are the small metal pipes that run through your AC unit. They snake around the inside of the unit, sitting in front of the fan.

Ice builds up on the coil’s surface for a few different reasons.

  1. The coil is too cold for a period that is too long.
  2. There isn’t enough air flowing over the coils to keep the ice from building up.
  3. The unit is damaged and needs to be replaced.

When To Call a Professional

When To Call A Professional

If your AC’s coils have frozen, the part of the unit that isn’t working is likely the indoor evaporator coils in the machine. You can unfreeze these yourself, and they exist in portable ACs, mini ACs, and standard window ACs.

Sometimes, it’s the refrigerant lines. You won’t be able to fix this by yourself because the refrigerant lines are built into the walls of your home.

If you have a built-in AC unit and cannot troubleshoot the issue causing your AC to blow out warm air or overheat, you need to call a contractor to check things out.


Most home AC units can be fixed without the help of a professional because they need to be defrosted.

Depending on your AC unit model, there may be a setting to help with this, or you can force enough cold air through the unit to unfreeze the evaporator coils.

Unfortunately, if your AC’s coils are inside your home’s walls, you will need a professional to come out and defrost them.

Frequently Asked Questions

Do I Need To Take Apart My AC To Unfreeze the Coil?

Though it can be tempting to start unscrewing things to look inside and check what’s happening, you shouldn’t need to do this. Before anything else, blast your AC without the thermostat on. This should fix the issue of a frozen coil for most units.

Why Are My AC’s Coils Frozen?

Most of the time, a set of frozen coils occurs due to a lack of airflow.

This can happen because your AC’s filter is dirty, the unit is blocked, or it’s too cold outside, and ice has built up on the surface of the coils.

Whatever the reason, you should be able to troubleshoot it and sort it out yourself. Provided you don’t own a unit with the coils in your walls.

Leave a Comment

Your email address will not be published. Required fields are marked *