How to Maintain Your Through-the-Wall AC: Filters, Coils, Drainage & Seasonal Tune-Ups
Most homeowners think wall ACs are “install it and forget it” systems.
Tony has lost count of how many wall units he’s pulled apart that were stuffed with dust, clogged with moldy coils, full of debris, or drowning in their own drainage.
Through-the-wall ACs are strong, reliable machines — when you maintain them.
Skip maintenance, and you’ll get:
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weak cooling
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high energy bills
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foul smells
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loud operation
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water leaks
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frozen coils
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early compressor failure
This is Tony’s complete real-world maintenance guide, the same checklist he uses on job sites to keep wall AC units running for 10–15 years.
Let’s keep your wall unit clean, quiet, and cold.
1. Filters: The #1 Maintenance Task (And the One Everyone Ignores)
Filters are the lungs of your AC.
A dirty filter suffocates airflow and forces the unit to work twice as hard.
Tony sees homeowners go months without cleaning filters.
That’s how you burn out a compressor or freeze a coil.
How Often Should You Clean the Filter?
✔ Every 30 days in summer
✔ Every 2 weeks if you have pets
✔ Every 2 weeks in dusty homes
✔ Every week during heat waves
How to Clean It:
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Remove the front grille
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Pull out the filter
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Vacuum both sides
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Rinse with warm water (no soap needed)
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Air-dry completely
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Put it back
A clean filter:
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boosts airflow
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reduces noise
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saves energy
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keeps coils from freezing
(Reference: Residential HVAC Load Calculation Standards)
2. Cleaning the Evaporator Coil (Inside Coil)
If the inside coil gets dirty, you’ll see:
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weak cooling
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ice buildup
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water leaks
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higher bills
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a cold room but hot adjacent areas
Tony recommends cleaning the coil once per season.
Signs Your Coil Is Dirty:
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reduced airflow
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musty smell
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sweating around the grille
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coil looks dusty or clogged
How to Clean It (Tony’s Method):
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Remove filter and front grille
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Use a coil brush OR soft nylon brush
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Brush in the direction of the fins (never sideways)
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Use an approved coil cleaner
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Rinse carefully
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Let it dry before running
Tony keeps coil fins straight — bent fins reduce efficiency dramatically.
(Reference: Home Insulation and Envelope Performance Manual)
3. Cleaning the Condenser Coil (Outside Coil)
The rear coil releases heat outside.
If it’s dirty, your AC will:
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run longer
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get louder
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fail earlier
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overheat
Wall units suck in outdoor dust, pollen, and grime, especially in cities.
How to Clean the Outside Coil:
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Remove exterior grill (if accessible)
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Vacuum loose debris
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Spray coil cleaner
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Rinse from inside-out to avoid packing dirt
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Let dry fully
How often?
✔ Once per season
✔ Twice per season in dusty areas
Dirty coils ruin efficiency more than any other problem.
4. Drainage: The Silent Culprit Behind Leaks, Mold, and Wall Damage
Poor drainage is Tony’s #1 maintenance problem.
Most homeowners don’t even know their wall AC has a drainage system.
Drainage Issues Cause:
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water dripping indoors
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mold growth
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bubbling paint
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rotten framing
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sleeve corrosion
Drainage Fix Checklist:
✔ Sleeve tilted slightly downward (¼ inch)
✔ Weep holes unclogged
✔ No debris inside rear cavity
✔ No insulation blocking drain path
✔ No standing water in base pan
✔ Sleeve not tilted inward
Tony clears drain paths every summer — it’s the quickest fix to prevent major water damage.
(Reference: Air Distribution and Duct Sizing Reference)
5. Deep Cleaning the Blower Wheel — The Most Overlooked Step
The blower wheel pushes air across the coil.
If it’s dirty, you’ll get:
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weak airflow
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loud whooshing
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inconsistent temperatures
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higher energy bills
Cleaning it is tricky but essential.
Tony’s Steps:
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Remove front panel
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Remove filter
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Access blower wheel (usually behind a panel)
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Brush off dust
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Use vacuum with brush attachment
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Wipe with a damp cloth
This should be done once per year for heavy-use units.
6. Checking for Air Leaks Around the Sleeve
Air leaks around the sleeve create:
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drafts
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humidity
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dust infiltration
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reduced cooling
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higher bills
Tony inspects:
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top & bottom edges
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corners
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insulation gaps
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foam wear
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wall-to-sleeve transitions
Then seals them with:
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HVAC-grade foam
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silicone
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weatherstripping
If your room feels humid, you probably have sleeve air gaps.
(Reference: Mechanical Noise Prevention and System Balancing Principles)
7. Checking the Electrical Connections
Wall units use significant power.
Loose or weak connections can cause:
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tripped breakers
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overheating
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wiring damage
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poor cooling
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burned capacitors
Tony checks:
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plug tightness
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outlet condition
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breaker amperage
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voltage stability
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wire gauge
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ground connection
This is especially important for heat pump and electric heat models.
8. Winterizing Your Wall AC (If You Live in a Cold Climate)
Tony winterizes wall ACs in cold states to prevent:
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drafts
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coil freezing
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cold backflow
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energy loss
Winterizing Steps:
✔ Install interior insulated cover
✔ Seal exterior vent
✔ Close blinds to add a thermal barrier
✔ Check sleeve insulation
✔ Use foam gasket if needed
Do NOT wrap the outside with plastic — that traps moisture and ruins the unit.
9. Spring Start-Up Checklist (Tony’s Pre-Season Routine)
Before running your AC for the first time each year, do this:
✔ Step 1: Clean the filter
✔ Step 2: Clean the indoor coil
✔ Step 3: Clean the outdoor coil
✔ Step 4: Clear the drainage holes
✔ Step 5: Check insulation inside sleeve
✔ Step 6: Tighten mounting screws
✔ Step 7: Test fan speeds
✔ Step 8: Check for unusual noises
A 20-minute spring tune-up can prevent 90% of summer breakdowns.
10. Summer Mid-Season Check (Tony’s Heat Wave Tune-Up)
Halfway through summer, Tony recommends:
✔ Clean filter again
✔ Inspect outdoor coil
✔ Verify unit cycles correctly
✔ Check for frost on coil
✔ Ensure adequate airflow
✔ Inspect sleeve for leaks
Most performance issues show up mid-season — this check keeps things under control.
11. Fall Shut-Down Routine
At the end of cooling season:
✔ Deep clean filter
✔ Clean coils thoroughly
✔ Check drainage for clogs
✔ Inspect for corrosion
✔ Seal interior gaps
✔ Winterize unit
This prevents mold and corrosion over winter.
12. When to Call a Professional (Tony Doesn’t Like Guesswork)
Some issues require a real tech:
❌ constant icing
❌ no cooling at all
❌ burnt smell
❌ electrical buzzing
❌ water leaking inside
❌ compressor short-cycling
❌ unusually loud or vibrating unit
❌ mold inside coil housing
Tony doesn’t want homeowners risking injury or causing wall damage.
13. Tony’s Final Verdict: A Clean Wall AC Is a Powerful Wall AC
Maintenance isn’t optional — it’s part of ownership.
With proper maintenance:
✔ cooler rooms
✔ lower bills
✔ quieter operation
✔ better airflow
✔ longer lifespan
✔ fewer repairs
✔ cleaner air
Without maintenance:
✘ weak cooling
✘ leaks
✘ noise
✘ odors
✘ high power bills
✘ coil failure
✘ unit burnout
Tony’s rule:
“A wall unit dies from neglect — never from cleaning.”
Do the basics and your system will last a decade or more.
We will see the brand comparison in the next blog.
