Jake’s Intro:
Yo, it’s Jake again 👋. And if your AC’s blowing warm air, cycling like it’s confused, or just plain underperforming, I’ve got some bad news: your evaporator coil might be leaking.
I hate to be the bearer of HVAC heartbreak, but these leaks are one of the top reasons I get emergency calls in the middle of July. They sneak up on you, they mess with your refrigerant levels, and they love to empty your wallet if you ignore ’em too long.
But don’t panic—we’re gonna go over what causes these leaks, how to sniff ‘em out (literally), and what your options are to fix or replace. Let’s get after it. 💪
What Exactly Is an Evaporator Coil Leak?
Your evaporator coil sits inside the air handler or furnace, quietly chilling the air that gets pumped into your home. It's filled with refrigerant, which absorbs heat from the air and cycles back to the condenser to release that heat outside.
But when that coil develops tiny pinholes or cracks, refrigerant leaks out. And without enough refrigerant, your system can’t cool anything—let alone keep you comfortable in a heat wave.
Over time, the leak gets worse. You’ll notice weaker airflow, higher energy bills, and eventually, no cold air at all. And that’s just the beginning.
Top Causes of Evaporator Coil Leaks (aka Coil Killers)
1. Formicary Corrosion (a.k.a. Ant Nest Corrosion) 🐜
This one’s the big villain. It’s caused by formic acid in the air—a byproduct of VOCs (volatile organic compounds) found in household products like cleaners, paint, or glue. When these chemicals mix with moisture and oxygen, they eat away at copper like termites on wood.
Over time, tiny pinholes form—usually too small to see—and your refrigerant starts leaking like a slow drip.
If you're curious about how it works, check out this deep dive by Alamo Austin Air on formicary corrosion and prevention.
2. Vibration and Physical Wear
Your system runs all the time. That means the coil is constantly expanding, contracting, and vibrating. Over the years, those little movements can wear down copper tubing—especially at bends or contact points—leading to mechanical leaks.
If your coil's rubbing against a metal bracket or has been poorly installed, the friction can eat right through the tubing.
3. Improper Installation
Hate to say it, but sometimes the “pro” who installed your coil took shortcuts. I’ve seen:
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Over-tightened brackets causing stress points
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Refrigerant overcharges or undercharges (leads to pressure issues)
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Lack of UV protection in sunny attic installs
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No coil coating in coastal areas (hello salt corrosion!)
Trust me, the cheapest install usually costs the most in the long run. 🙄
4. Electrolysis
Yep, your coil could be getting zapped. If copper coils touch dissimilar metals or if your unit has grounding issues, electrical currents can corrode the tubing over time. This one’s rare but brutal.
Want to geek out more? MACS has excellent resources on electrochemical damage in HVAC systems.
Early Signs You’ve Got a Leak (Before It’s a Full Meltdown)
Spotting a leak early can save your system—and your bank account. Watch for:
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Warm air blowing from vents, even when thermostat is set to “cool”
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Hissing or bubbling noises (especially at startup)
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Ice forming on the coil or refrigerant lines
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Unusually high energy bills
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Frequent need to add refrigerant (this is a BIG red flag)
Still unsure? A licensed tech can test your system using a UV dye or electronic leak detector (aka the HVAC sniffer). This guide from PV HVAC goes into all the pro methods used in the field.
Should You Repair or Replace?
Alright, here’s the million-dollar question: Can I patch the leak or do I have to replace the whole coil?
Repair (✅ Possible but Rare):
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Good if the leak is tiny and accessible
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May involve soldering or epoxy sealants
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Still needs system to be vacuumed and recharged with refrigerant
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Usually temporary
Use repair as a band-aid, not a cure. I've patched coils for customers who just needed a few months of cool air before replacing the whole system—but long-term? Not worth it.
Replace (✅ Recommended in Most Cases):
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Essential if the coil is out of warranty
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Necessary for multiple pinholes or corrosion
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Lets you upgrade to an R-32 compatible model
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Comes with a new warranty and efficiency bump
John C. Flood lays out when you should replace a leaky coil vs trying to stretch it.
Tips to Prevent Future Leaks
You can’t completely stop a leak from ever happening—but you can stack the odds in your favor:
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Use coated coils if you live near saltwater or in high-humidity areas
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Keep your indoor air clean—ventilate, avoid strong VOC cleaners, and use quality air filters
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Check that your drain lines are clear and your pan isn’t overflowing
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Install a whole-home dehumidifier to reduce moisture in the air
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Ask your HVAC tech about UV protection and anti-corrosion treatments
Bonus: If you’re doing a new install, go for an aluminum coil—they’re more resistant to corrosion than copper, though less common.
How Much Does It Cost to Fix or Replace a Leaky Coil?
Here’s the ballpark:
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Leak detection & recharge: $200–$600
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Temporary repair (epoxy, soldering): $250–$700
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Full coil replacement (including labor): $800–$2,500
But if your system’s 8+ years old, replacing the coil often makes more sense—especially if it helps you upgrade to a high-efficiency system that uses R-32.
Jake’s Take on Where to Shop for a New Coil 🔧
If you’re gonna bite the bullet and replace, don’t just grab the first coil you see online. You want:
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A brand-certified match (especially Goodman if that’s your current setup)
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R-32 ready (future-proof your system)
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Correct size & orientation
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Warranty included
That’s why I always recommend starting with The Furnace Outlet’s evaporator coil collection. You’ll find:
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Coils from trusted brands
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Matching info right on the product page
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Detailed specs for SEER, tonnage, refrigerant, and airflow
And if you’re unsure? Give them a shout—they actually know HVAC, not just warehouse inventory.
Jake’s Wrap-Up 🛠️
Alright, let’s land this plane. Leaky evaporator coils aren’t just an HVAC hiccup—they’re a full-on system wrecker if you don’t catch ’em early. Whether it’s corrosion, vibration, or just time doing its thing, once that coil starts leaking refrigerant, your AC’s on borrowed time. 🕒
Now you know what causes those pesky leaks, how to spot the signs, and when it makes sense to fix versus replace. More importantly, you know not to keep refilling refrigerant like it’s windshield wiper fluid and hope for the best (trust me, I’ve seen folks try that).
If it’s time to upgrade your coil, don’t overthink it. Head over to The Furnace Outlet’s full evaporator coil lineup and get something that’s built to last. They’ve got vertical, horizontal, and downflow coils—plus R-32 compatible options ready to future-proof your system. And yeah, the prices are better than what most supply houses will quote you.
Need some cleaning tips for your evaporator coils? Visit my guide: Coil Me Maybe?
Bottom line? Take care of your coil, and it’ll take care of your comfort. Ignore it, and you’re looking at sweaty afternoons and an angry bank account. Let’s not go there.
Catch you next time,
Jake out. 🔧🍻
