Hey folks, it’s Mike again 👋
Ever walk past your indoor unit and think, “Why does this thing sound like it’s working overtime—but it still feels like a sauna in here?” You open it up and—bam!—your evaporator coil looks like it’s been dipped in liquid nitrogen. ❄️
I’ve seen frozen coils in basements, closets, attics, you name it—and nine times outta ten, it’s fixable without shelling out for a whole new system. In today’s blog, I’m going to break it down real simple: why your coil’s freezing up, what to do about it, and how to keep it from happening again.
Let’s get into it. 🧊🧰
What’s an Evaporator Coil Supposed to Do (When It’s Not Pretending to Be an Ice Rink)?
Your evaporator coil’s job is to absorb heat from the air inside your home. It’s part of the cooling loop: warm air passes over the cold coil, heat gets sucked out, and cooler air gets pushed back through your vents. When it’s working right, you don’t even know it’s there.
But if that balance gets thrown off—like, say, there’s not enough heat hitting the coil—it gets too cold and freezes up. And no, this isn’t just a minor inconvenience. A frozen coil can kill your compressor if you ignore it too long.
For a quick refresh on how the whole system works together, this explainer from Carrier is solid.
The 6 Main Reasons Your Evaporator Coil Is Freezing Up
1. Low Airflow = Low Heat Transfer
When not enough air moves over the coil, it doesn’t get the heat it needs to stay above freezing. That’s like running your fridge with the door open—everything just ices over.
Common airflow killers:
-
Dirty air filter 😷
-
Blocked vents or returns
-
Blower fan issues
-
Collapsed ductwork
Step one: Check and change your filter. If it looks like a lint trap from a 1980s dryer, you’ve found your first problem.
2. Refrigerant’s Too Low
Refrigerant absorbs heat. When you don’t have enough of it in the system, the coil gets too cold and turns into a popsicle. This is usually caused by a leak—and no, refrigerant doesn’t just “run out” like gas in a car.
Need a deeper dive? Energy.gov covers why low refrigerant is a big deal and what causes it.
3. Thermostat Set Too Low
Set your thermostat too low for too long, and you’re asking for trouble. Your system will run constantly trying to hit a temperature it can’t reasonably maintain.
Tip from Mike: Don’t set it lower than 68°F overnight, especially in humid climates. You’re just creating ice, not comfort.
4. Dirty Evaporator Coil
Dust, pet dander, and tobacco smoke can all cling to your coil like gum on a boot. If your coil’s dirty, airflow and heat transfer take a nosedive.
Want to clean it yourself? This guide from Trane walks you through it without breaking anything.
5. Faulty Blower Motor or Relay
Your blower fan needs to run strong to keep air moving. If the motor’s weak or the relay isn’t kicking it on, you’ll have a still coil and frozen pipes.
Warning signs: Weird hums, weak airflow, or a fan that won’t stop running—or won’t run at all.
6. Drain Line Clogged
This one’s sneaky. When the drain pan overflows, moisture can splash onto the coil, mix with the cold metal, and freeze everything up. Bonus: mold and mildew love it.
Step-by-Step: How to Fix a Frozen Evaporator Coil (Without Losing Your Cool)
Step 1: Shut It All Down 🔌
Turn off the AC at the thermostat and the breaker. Running the system while frozen can kill your compressor faster than you can say “warranty void.”
Step 2: Let It Thaw Naturally
Open the access panel and let warm air get in. Don’t use a hair dryer—it can warp plastic parts and damage fins. Depending on how bad it is, thawing may take a few hours to overnight.
Step 3: Swap Out the Air Filter
Even if it looks okay, change it. Filters are cheap. Compressors aren’t.
Step 4: Check Airflow and Vents
Open all vents, make sure furniture isn’t blocking anything, and check for disconnected or crushed ductwork.
Step 5: Clean the Coil (If You Can Reach It Safely)
Spray on a no-rinse evaporator coil cleaner and gently brush away dust and debris. Don’t use high-pressure air or water.
For help choosing a cleaner, this article from Goodway compares the best coil cleaners for homeowners.
Step 6: Fire It Back Up
Once the coil’s dry, power everything back on and monitor it. If the ice returns quickly, you may have a leak or blower issue—time to call a pro.
When to Call in a Tech 🛑
There’s no shame in waving the white flag when:
-
Ice keeps returning every few days
-
Your refrigerant level is low
-
The blower motor won’t kick on
-
Your unit is more than 10–15 years old
Need help finding a qualified technician? The ACCA Contractor Locator helps you find certified folks near you.
Preventing Coil Freeze-Ups for Good 🧼🌀
Mike’s top tips:
-
Change your filter every 1–2 months (more often if you’ve got pets or allergies)
-
Keep vents open in every room—even the guest room you never use
-
Have your system serviced annually (spring is best)
-
Inspect the coil and drain pan regularly
-
Don’t crank your thermostat lower than needed
And for folks who are serious about efficiency, upgrading to a new, properly matched coil can make a world of difference. I always recommend starting your search with The Furnace Outlet’s full evaporator coil collection. They carry everything from compact 2-ton coils to beefy 5-ton setups—all R-32 ready and backed by solid manufacturer warranties.
Final Word from Mike – Don’t Let Jack Frost Move Into Your Air Handler ❄️👴
Here’s the deal: a frozen evaporator coil isn’t just annoying—it’s a sign that your system is begging for attention. Whether it’s a clogged filter, low refrigerant, or airflow problems, freezing coils are your HVAC system’s cry for help.
But now? You know what to look for. You know how to thaw it. And if the problem’s bigger than a dirty filter or a stubborn vent, you know where to go to get a replacement coil that’ll keep things running right:
👉 The Furnace Outlet – Evaporator Coils Collection
Worried about positioning your coils correctly? Visit: Standing Tall or Laying Low?
Keep it simple. Keep it maintained. And keep your cool all season long.
Catch you on the next one,
– Mike, your cool HVAC guide
