Introduction
Hey, Mike Sanders here. Installing a through-the-wall air conditioner is a smart move for targeted cooling in bedrooms, offices, or smaller spaces. But after the install is over, your AC will need regular attention to stay in top shape.
As an HVAC pro who’s seen the good, the bad, and the ugly, I can’t stress enough how important routine maintenance is. Even small things — like a dirty filter — can make your unit work harder and rack up your energy bills. And when you do run into a hiccup, knowing a few basic troubleshooting tricks can save you a repair bill or help you explain the issue clearly if you call a technician.
In this article, I’ll give you the full rundown:
✅ How to clean and care for your through-the-wall unit
✅ Common troubleshooting steps for typical problems
✅ Signs you need professional help
Let’s jump in.
🧹 Why Routine Maintenance Is Essential
Your through-the-wall AC contains moving parts, refrigerant, a compressor, fans, and filters — all of which need to be cleaned or checked to prevent wear and tear. Proper maintenance:
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Reduces energy consumption
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Extends your unit’s lifespan
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Improves indoor air quality
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Prevents costly breakdowns
If you want to go deeper into why maintenance matters, the EPA has a detailed article on maintaining heating and cooling equipment that’s well worth a read.
🧰 DIY Maintenance Tasks You Can Do Yourself
You don’t need to be a pro to keep your through-the-wall unit running efficiently. Here are my top recommended tasks:
1️⃣ Clean or Replace the Filter
The filter is your AC’s first line of defense against dust and debris. A clogged filter restricts airflow, reducing cooling power and making the compressor work harder.
How often? Every 1–2 months during heavy use.
How to do it:
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Open the front panel of your unit.
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Gently slide the filter out.
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Rinse under lukewarm water and let it dry completely.
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Or, if it’s damaged, replace it with the model specified in the owner’s manual.
If you’d like to understand the role of filters better, check out the U.S. Department of Energy’s air filter guide.
2️⃣ Clean the Coils and Vents
Your unit’s evaporator and condenser coils also accumulate dust over time. This buildup reduces heat transfer and efficiency.
Steps:
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Turn off the power to your unit.
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Remove the outer cover.
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Gently vacuum or use a soft brush to clean dust from coils and fins.
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Be careful not to bend or damage the fins.
Cleaning the coils can also prevent freezing and help the unit last longer.
3️⃣ Inspect and Seal Around the Sleeve
Check around your wall sleeve and unit for any gaps or cracks. If you feel drafts, apply exterior-grade caulk or foam sealant to keep moisture and air out. Poor sealing can cause water leaks and energy loss.
4️⃣ Check the Drainage
Your AC dehumidifies as it cools. Ensure the drain holes or tube at the bottom of the unit is clear so water can drain properly. If water pools inside the unit, it can lead to rust or even mold growth.
5️⃣ Test the Thermostat Controls
Periodically, test the thermostat on your AC to ensure it’s reading the temperature accurately and cycling the unit on and off properly. An incorrect thermostat can cause the AC to run too long, freeze up, or not cool enough.
🔍 Common Troubleshooting Steps
Even with good maintenance habits, you may run into some common issues. Here’s how to troubleshoot them yourself.
❄️ AC Runs But Doesn’t Cool Enough
Possible causes:
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Dirty filter or coils
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Thermostat set too high
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Low refrigerant
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Obstructed outside air flow
DIY fix:
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Clean the filter and coils
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Lower the thermostat by 5 degrees and wait 10–15 minutes
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Remove anything blocking the outside part of the unit, like furniture or vegetation
If these steps don’t work, it could be a refrigerant leak or compressor issue — time to call a pro.
🔊 Unusual Noises
Your unit might hum, rattle, or buzz.
Possible causes:
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Loose screws or panel
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Bent fan blade
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Debris inside the unit
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Worn-out compressor
DIY fix:
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Turn off the unit and check the cover, screws, and inside the fan area for loose parts or debris.
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Tighten what you can access.
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Don’t attempt to fix compressor noise — leave that to a technician.
💧 Water Leaks Inside
Possible causes:
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Poor drainage due to a blocked drain tube
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Unit tilted inward instead of slightly sloping outside
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Damaged seals
DIY fix:
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Check and clean the drain tube.
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Adjust the unit so it slopes slightly toward the outside.
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Reseal around the sleeve with caulk if it looks cracked.
⚡ Unit Doesn’t Turn On
Possible causes:
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Tripped breaker
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Unplugged unit
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Faulty thermostat
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Burnt-out capacitor
DIY fix:
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Check the power cord and outlet.
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Reset the breaker.
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Test the thermostat with new batteries.
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Call a professional if electrical issues persist.
If you’d like a deeper look into AC electrical issues, Family Handyman offers a helpful article on basic AC troubleshooting.
🧑🔧 When to Call a Professional
Some AC repairs require specialized tools and knowledge — especially if they involve refrigerant handling, electrical wiring, or the compressor.
Here are some signs you need an expert:
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Warm air despite proper maintenance
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Ice buildup on coils
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Burning smells or loud banging noises
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Frequent short-cycling
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Increased energy bills without other explanation
In these cases, contact a licensed HVAC technician. The Air Conditioning Contractors of America can help you find a certified professional in your area.
🕰️ Scheduling Annual Maintenance
Even with your own maintenance, an annual checkup by a pro is money well spent. A technician will inspect all components — refrigerant level, wiring, fan motors, etc. — to catch problems before they worsen.
Your tech will also check for refrigerant leaks and recharges if needed, which only a licensed pro can do under the law.
🌳 Energy Efficiency and Long-Term Care
Your through-the-wall AC will last longer and use less power if you treat it right. Regular maintenance can improve your unit's efficiency by up to 15%. To dig into energy-efficient cooling strategies, take a look at the Energy Star's AC buying and maintenance guide.
And don’t forget that newer refrigerants like R-32 — which you’ll find in many models on The Furnace Outlet — also help reduce your unit’s environmental footprint while offering powerful cooling.
✅ Final Thoughts
Your through-the-wall air conditioner doesn’t require rocket science to keep humming along — just some regular attention and a proactive mindset. With a clean filter, debris-free coils, a clear drain, and prompt troubleshooting, most minor issues can be avoided or fixed quickly.
And if something looks or sounds serious, don’t hesitate to call a pro. Keeping up with your AC pays off in lower bills, better comfort, and a longer lifespan for your unit.
If you’re looking for a new through-the-wall unit or need replacement parts, explore the full selection at The Furnace Outlet. We have a variety of models and BTU sizes to suit any home.
