Air Conditioner Keeps Freezing Up? Here’s How to Fix It

How bizarre! It’s 100 degrees in the shade, and you’re wondering why your house is getting hot. You head outside and see that your air conditioner is freezing up.

How can that be?

Actually, it’s fairly common. But yes, still bizarre. How could such a thing happen?

It could happen for several reasons. It could be your filter—because any problem can be due to the filter! Or it could be something serious like a refrigerant leak.

I’ll provide a complete list below, plus possible solutions—if there are any. So read on.

Solving A Freezing Air Conditioner

Let’s start with the simpler things—or at least things you should be able to troubleshoot and fix yourself. Then I’ll move on to issues that will likely need a pro to fix.

1. Dirty Air Filters

For such a cheap part—at least in comparison to your other HVAC equipment—the air filter can cause all sorts of problems.

Actually, it’s not the filter. It’s homeowners not doing regular maintenance and changing or cleaning the filter.

The filter’s job is to catch particles in the air before they enter your ducts and ultimately pass into your air conditioner. Because the debris can destroy the motor. However, if left unattended, that same filter can also destroy your blower motor.

Why?

Because as dirt and debris build up on the filter, it blocks or restricts airflow into your system. Ultimately, condensation starts to build up on the evaporator coil.

The air conditioner is expecting airflow to carry away the cold air temperatures it’s producing. The lack of warm airflow causes the refrigerant temperature to drop below freezing – which begins to cause the condensation to freeze... which further restricts airflow. Eventually causing a total air conditioner freeze up.

Solution: Change your filters! Depending on your system and your filter of choice, this may need to be done every three months. Maybe less, maybe more.

2. Dirty Air Ducts

Who hasn’t got the air duct cleaning telemarketing spam call a time or a hundred?

Most of the time you can just hang up, secure in the knowledge you don’t need your ducts cleaned.

However, there are times they may need to be cleaned.

• Have you recently done any sort of reno or construction in your home?
• Do you have a big family with lots of kids, pets, and dirt?
• Have you just moved into a resale home?

Just as dirty filters will impede airflow, so will a buildup of dirt in your ducts. Again, this will eventually cause your evaporator coil to freeze up.

Solution: Construction typically leaves a lot of dust behind, and that will find its way through your ductwork.

Big families and pets can create a lot of dust and debris, so cleaning your ducts every 3 or 4 years may not be a bad idea.

If you’ve just moved in, you have no idea when they were cleaned the last time, if ever. So getting them checked and cleaned is just a smart idea.

3. Bent or Dirty Evaporator Fins

Yes, dirt is the culprit yet again.

If too much dirt builds up on the fins of your evaporator, it can’t absorb enough heat from the air. The air restriction will cause Freon temperatures to drop below freezing, which freezes the condensation and causes a large buildup.

The same thing can happen if the fins get bent.

Since your air conditioner unit is sitting outside, unprotected from the elements, it can get hit by hail, blowing branches, and anything else heavy enough to damage them. Even toys and balls. While many parts of the air conditioner can take a knock, damage to the evaporator coils can’t!

Also, your air conditioner unit isn’t to be used as a prop for things like your bicycle. Anything that can damage the fins should be kept at a distance.

Solution: Before you start cleaning, make sure to turn to power to your AC off. You’ll either have a breaker outside near your unit or you’ll need to shut off the breaker at your main panel inside.

• Clean around the outside of the unit and then remove the top grate carefully. The fan, and perhaps the motor as well, is attached to it.
• Remove any dirt that has collected at the bottom, either by hand or with a shop vac.
• Inspect for damage to the fins. Some may be bent, so they should be straightened out.

For those of you who prefer visual instructions, check out this video.

4. Closed or Blocked Vents

When we talked about filters—and even the condenser—the problem caused by the buildup of dirt was reduced airflow.

Guess what? Putting the sofa in front of a return air vent or closing a supply vent off can do the same. Every system has specific airflow requirements. When it doesn’t get what it needs, bad things happen. Expensive things happen.

Solution: Don’t block return vents. They’re typically on a wall, not far from the floor, so this might be a challenge. But they are not supposed to be blocked.

Don’t close your supply registers all the way. They’re fine to partially close but allow for some airflow.

Turn the thermostat to the off or Fan setting, make sure all your grates and vents are open and accessible, and wait until the coil thaws out. Once the ice is gone, you can try partially closing a supply vent or two to see if it starts to ice over again. If it does, you have your answer. You need to keep them open.

5. Refrigerant Leak

Has the ice formed on the side panels of your AC unit? Then you could have a leak. The second thing you might notice is a hissing sound.

Solution: This isn’t something the homeowner can deal with. Only certified technicians are legally allowed to deal with refrigerants.

6. It’s Cold Outside

Have you lost your mind and put the AC on when the outside temps are less than 62 degrees F / 0 C? This will cause a pressure drop and may cause any condensation to freeze.

Solution: If it’s winter, and your house is hot for some reason, open the windows. Do not turn on the AC.

7. Damaged or Dying Blower Fan/Motor

It’s not common, but your blower fan can break. Or your motor can break down.

Problems with either the fan or the motor will impact airflow, which again can cause your AC to freeze up as the condensation starts to freeze.

Solution: If your fan is noisy, or not running at all, you’ll need to call a technician to inspect your system.

Conclusion

It might seem bizarre to see your AC frozen over in the heat of summer, but as detailed above, there are several reasons why it could happen.

• Dirty air filters
• Dirty air ducts
• Bent or dirty condenser fins
• Closed or blocked vents
• Refrigerant leak
• It’s cold outside
• Blocked condensate line
• Damaged or dying blower fan/motor

In most cases, there is something you can do to stop it from happening again, but in some cases, it will mean a call to a pro and perhaps a large bill to get it fixed.

The best thing to do is keep up with your maintenance—and don’t close or block vents. Follow these instructions, and you should be fine.

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