Introduction
Hey there, it’s Jake Lawson. If you’re like most homeowners, you probably take your through-the-wall air conditioner for granted until one scorching afternoon when it just doesn’t cool like it used to. The good news is that most issues can be avoided — or fixed — with the right maintenance habits and a few quick troubleshooting tricks.
In this article, I’ll cover everything you need to know about extending the lifespan of your through-the-wall AC, including easy cleaning routines, the most common issues and solutions, safety considerations, and some pro tips you won’t find in most owner’s manuals.
By the end of this guide, you’ll have a clear plan to keep your AC in top condition for years to come.
Why Routine Maintenance Matters
Your through-the-wall AC is a hardworking appliance. Every day, it’s cycling warm, humid air into crisp, comfortable living space — and over time, dust, debris, and wear can impact its efficiency.
According to the U.S. Department of Energy, proper maintenance can improve cooling performance and lower energy consumption by as much as 15% (read more on that at the Department of Energy’s air conditioning page). That’s not just an energy savings — it’s less wear and tear on the unit, helping you put off an expensive replacement.
Essential Maintenance Tasks for Longer AC Life
Let’s go step-by-step through the most important tasks you can do as a homeowner to keep your through-the-wall AC working like new.
🧹 1. Clean or Replace Filters Regularly
Your AC’s filter is its first line of defense against dust, allergens, and particles. But clogged filters restrict airflow and cause your AC to work harder, which can overheat the compressor or lead to ice buildup.
How often?
Every 4–6 weeks during peak cooling months — more often if you have pets, live in a dusty area, or run the AC 24/7.
What to do:
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Turn the unit off and carefully slide out the filter.
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If washable, rinse with warm water and let dry completely before reinserting.
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Replace disposable filters as needed with manufacturer-approved options.
💡 Quick Tip: Check the filter monthly; if you can’t see light through it, it’s time to clean or replace.
🧽 2. Keep the Coils Clean
Your AC has two sets of coils:
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Evaporator coils (inside the room)
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Condenser coils (outside the wall)
When these coils accumulate dirt, they reduce heat exchange and strain the system.
Cleaning:
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Shut off power.
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Use a soft brush or vacuum to gently clean accessible coils.
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Consider a professional coil cleaning service every 1–2 years — especially for the outdoor condenser. Check the EPA’s coil maintenance guidelines for best practices.
🧰 3. Check and Straighten Fins
Both sets of coils have delicate aluminum fins that can bend easily, restricting airflow.
Use a fin comb to straighten any bent fins — this improves air movement and cooling efficiency.
🧽 4. Keep the Drain Clear
Your AC unit extracts moisture from the air as it cools — this water must drain properly.
If the drain hole or drain tube is clogged, water can back up into the unit or inside your wall.
What to do:
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Check the drain hole at the bottom of the unit.
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Run a small wire or pipe cleaner through the drain to clear clogs.
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Make sure the outside part of the unit is slightly tilted downward so water can drain outside properly.
🔧 5. Inspect Insulation and Wall Sleeve
Check the insulation around your wall sleeve and window framing regularly for cracks or gaps. Proper insulation prevents air leaks and keeps your AC working efficiently.
You can use affordable foam tape or caulking to seal any gaps.
Common Problems & Troubleshooting Tips
Despite regular maintenance, your AC might occasionally act up. Don’t panic — most issues are surprisingly easy to troubleshoot. Let’s look at the most common ones.
❄️ 1. AC Not Cooling Properly
If your AC is running but blowing warm air, try these quick fixes:
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Check thermostat settings. Make sure it’s on “Cool” and set to a temperature lower than room temperature.
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Clean or replace the filter. Restricted airflow can cause the evaporator coil to freeze.
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Examine the outdoor condenser. Clear away any debris or weeds surrounding the outside part of the unit.
Still not working? The refrigerant may be low — in this case, you’ll need a pro to check refrigerant levels per guidelines from ASHRAE’s refrigerants guidance.
💧 2. Water Leaking Inside
Water dripping into your home usually indicates a clogged drain or improper tilt.
First, make sure the unit is slanted slightly toward the outside.
Then clear any debris in the drain hole or drain tube.
If water still leaks, inspect the sleeve’s weather seal and ensure it hasn’t degraded over time.
🧰 3. AC Won’t Turn On
If your unit isn’t responding:
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Check the power source. Confirm the AC is plugged into a working outlet.
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Inspect the circuit breaker. Reset if it’s tripped.
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Test the remote and batteries. Dead batteries can make it seem like your AC isn’t responding.
If the issue persists, contact a professional to check for electrical or control board issues.
🔊 4. Strange Noises
If you hear:
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Rattling: Likely a loose part or debris trapped inside.
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Buzzing: Could be electrical; turn off immediately and contact a pro.
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Squealing: Probably a worn fan belt — may require replacement.
In most cases, a quick tightening of screws or removing debris will solve the issue.
For a more detailed checklist of common AC noise causes and solutions, check out Family Handyman’s AC noise troubleshooting guide.
Proactive Practices to Avoid Big Repairs
Beyond the basics, there are a few proactive habits that can help you catch small problems before they become expensive.
🕰️ Schedule Seasonal Inspections
Before the summer heat ramps up, have a certified technician inspect your unit.
They’ll check refrigerant levels, test electrical components, and verify that all moving parts are properly lubricated — this can prevent midseason breakdowns.
🌳 Keep the Surrounding Area Clear
If your unit extends into a patio, deck, or garden, make sure there’s at least 12–24 inches of clear space around the outdoor part of the unit for airflow.
Trim shrubs, sweep away debris, and remove leaves or grass clippings.
📅 Stick to a Cleaning Calendar
Write down or set a phone reminder for monthly filter checks and annual coil cleanings.
Staying on schedule is the easiest way to extend the lifespan of your AC.
When to Call a Pro
While most maintenance and minor troubleshooting can be handled yourself, some issues require professional help:
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Refrigerant leaks
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Major electrical faults
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Compressor failure
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Persistent water leaks despite draining and tilt adjustments
If you notice these, it’s best to call an HVAC pro who’s trained in safe repair practices — especially when working with newer refrigerants like R-32. The EPA’s refrigerant handling guidelines (read them here) stress the need for proper certification before dealing with refrigerants.
Extending Lifespan = Saving Money
Through-the-wall ACs can last up to 10–15 years with proper care — much longer than a neglected unit.
By keeping up with small maintenance tasks and acting quickly to address issues as they arise, you’ll:
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Avoid surprise repair bills.
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Lower your energy use.
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Improve comfort in your home.
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Prevent expensive early replacement.
Ready to Upgrade?
And when the time eventually comes for a new unit, you’ll want to choose a quality, energy-efficient model that fits your wall sleeve perfectly.
That’s where I recommend browsing The Furnace Outlet’s through-the-wall air conditioners collection — you’ll find top brands and expert guidance to make the best choice.
Conclusion
Your through-the-wall AC is more than a cooling machine — it’s an investment in your comfort. Treating it right with regular cleaning, simple troubleshooting, and proactive care will add years to its lifespan and keep it running efficiently.
So, put a few of these maintenance tips into practice starting today.
Your future self — and your wallet — will thank you!
And if you ever hit a snag or want to explore an upgrade, don’t hesitate to reach out.
Happy cooling!
