How much does evaporator coil cleaning cost?
$249 for an easily accessible A-frame coil in the attic or closet. Up to $489 for coils that are sealed in and require sheet-metal removal to access. Includes drain pan treatment.
San Antonio · Evaporator Coil Cleaning Repair · Family-Owned Since 1996
The Indoor Coil Above Your Furnace Is Black With Mold. That's Why Your House Smells And Your AC Is Weak.
The evaporator coil — the A-frame above your furnace or in your air handler — collects condensation, dust, and biofilm. Once it's coated, airflow drops, smell builds, and capacity falls 20–40%.
Typical price
$249–$489
Time to fix
1.5–3 hours
Urgency
Medium — sooner if you smell mustiness through the vents
In plain English — what's going on with your evaporator coil cleaning
The evaporator coil is where the actual cooling happens inside your house. Cold refrigerant runs through it, your blower pushes warm air across it, and water condenses on the fins and runs down to the drain. That constant moisture, plus the dust that gets past your filter, turns into biofilm — black mold and slime that coats the fins.
Once that coating builds up, three bad things happen: airflow drops because the gaps between fins are clogged, heat transfer drops because there's an insulating layer on the metal, and the AC starts blowing musty-smelling air through the whole house.
Real evaporator coil cleaning means pulling the coil access panel (sometimes the coil itself if it's bad enough), foaming with a no-rinse evaporator-specific cleaner, and treating the drain pan and line. $249–$489 depending on access and severity. Skipping it costs you on capacity and on your family's air quality.
What it costs in San Antonio
$249–$489 — Price varies by coil access (some coils are sealed in and require sheet-metal work to reach). Our $59 diagnostic is waived when you approve the repair, so you only pay for the fix itself.
Symptoms you'll notice at home
If two or more of these sound familiar, it's probably your evaporator coil cleaning.
Musty or dirty-sock smell from the vents when AC kicks on
House isn't cooling as well as last year despite no obvious problems
Allergy symptoms or coughing that worsens with AC running
Water in the secondary drain pan or float switch tripping
Indoor coil keeps freezing despite proper refrigerant charge
Filter is clean but airflow at the vents is weak
Why evaporator coil cleanings fail in San Antonio
- Cheap fiberglass filters letting dust pass through onto the coil.
- High humidity in unconditioned attics keeping the coil constantly wet.
- No annual maintenance — coil hasn't been opened up and inspected in years.
- UV light missing or burned out (UV kills the biofilm before it builds up).
- Oversized AC that short-cycles, leaving the coil wet without drying out.
How we diagnose and replace it
Here's exactly what a Carnes and Sons tech does at your house — no mystery, no upselling.
- 1
Open the coil access panel and inspect
We photograph the coil so you see exactly what we see. Black biofilm, rusted fins, blocked drain pan — all documented.
- 2
Apply no-rinse evaporator coil cleaner
We use a foam designed for indoor coils that condensate carries away — no chemicals blow into your ductwork.
- 3
Flush the drain pan and line
The drain pan gets a separate treatment with biocide tablets, and the drain line gets flushed with nitrogen or vacuum to clear sludge.
- 4
Measure temperature split and static pressure
A properly cleaned coil pulls a 18–22°F temperature split. We document the before/after numbers so you see the recovery.
What Your Neighbors Are Saying
Get Your Evaporator Coil Cleaning Diagnosed Today
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Evaporator Coil Cleaning questions San Antonio homeowners actually ask
Why does my AC smell musty?
Almost always the evaporator coil. Biofilm on the wet fins grows mold and bacteria. When the blower kicks on, it pushes that smell into every room. Cleaning the coil and treating the drain fixes it in one visit.
Can I clean it myself?
No — the coil is delicate aluminum, and the wrong cleaner will eat the fins and contaminate your indoor air. Plus, most coils aren't accessible without taking the cabinet apart. Leave this one to a tech.
How often should the indoor coil be cleaned?
Inspected every year, cleaned every 2–3 years for most San Antonio homes. Sooner if you have pets, smokers, or run cheap filters.
Will a UV light prevent this?
Yes — a properly placed UV bulb kills the biofilm before it grows. We install them for $385–$485 and they last 2 years per bulb. If you've cleaned coils twice in five years, a UV light pays for itself.
Will cleaning fix my weak airflow?
If the coil is the bottleneck, yes — sometimes dramatically. We measure static pressure before and after so you'll see the recovery. If the duct system is also undersized we'll point that out.
How long does it take?
Anywhere from 90 minutes to 3 hours depending on how the coil is installed and how bad the buildup is. We'll give you a real time estimate before we start.
Do you treat the drain line at the same time?
Yes — drain pan biocide tablets and a full drain-line flush are included. A clogged drain is what trips most float switches and shuts your AC off.
Serving evaporator coil cleaning repairs across the greater San Antonio area
We're based in Stone Oak and roll trucks across San Antonio and the surrounding Hill Country every day.
Carnes and Sons Air Conditioning
License TACLB29435E · Family-Owned Since 1996
401 E Sonterra Blvd Suite 375
San Antonio, TX 78258(210) 600-5091
San Antonio, TX 78258(210) 600-5091
Mon–Sat: 7AM – 8PM · Emergency same-day service
Cities & neighborhoods we serve
San Antonio · Stone Oak · Alamo Heights · Hollywood Park · Hill Country Village · Shavano Park · Castle Hills · Leon Valley · Helotes · Boerne · Fair Oaks Ranch · Bulverde · Timberwood Park · Garden Ridge · Schertz · Cibolo · Selma · Universal City · Live Oak · Converse · Windcrest · New Braunfels
Talk to a real person about your evaporator coil cleaning
No call center. The owner or one of his sons picks up.
(210) 600-5091