How to Maintain Your Through-the-Wall AC: Filters, Coils, and Seasonal Tips

🏠 Why Regular Maintenance Matters for Wall Units

Through-the-wall air conditioners (TTW ACs) are built for durability and efficiency, but like any HVAC system, they require consistent maintenance to perform at their best. Skipping basic upkeep can lead to:

• Decreased energy efficiency

• Reduced cooling power

• Mold or mildew buildup

• Premature system failure

According to Energy Star, a dirty filter alone can increase energy consumption by 5%–15%. In this guide, we’ll walk you through the essential maintenance steps you should take by season, including filter care, coil cleaning, and how to prep your unit for both summer and winter.

🧼 Cleaning the Filter: Your First Line of Defense

🔁 How Often Should You Clean or Replace the Filter?

• Monthly during high-use seasons (summer/winter)

• Every 2–3 months during low-use times

• Immediately if airflow seems weak or odors are present

Reusable filters can typically be cleaned with warm water and mild detergent, while disposable ones should be replaced entirely.

✅ Step-by-Step: How to Clean a TTW AC Filter

1. Turn off and unplug the unit

2. Remove the front grille and pull out the filter

3. Vacuum loose debris using a soft brush attachment

4. Soak in a solution of warm water and a few drops of dish soap

5. Rinse thoroughly and let dry completely before reinstalling

👉 Pro Tip: Never run your unit without the filter. Dust and particles will quickly coat the internal coils.

🌀 Evaporator & Condenser Coils: Keeping Them Clean

🔍 What Happens When Coils Get Dirty?

When coils are clogged, your AC has to work harder to pull in air and cool it down — significantly reducing system efficiency. Dirty coils also promote mold growth and foul odors.

🛠️ DIY Coil Cleaning Tips

• Evaporator coils are located inside, behind the air filter

• Condenser coils are on the exterior part of the unit (behind or outside the wall)

Materials Needed:

• Fin comb or soft brush

• Coil cleaner (available at hardware stores)

• Spray bottle with water

Steps:

1. Remove any casing or panel blocking the coils

2. Spray with coil cleaner and let sit for 10–15 minutes

3. Wipe or rinse gently without bending the fins

4. Allow to dry completely before reassembling

📚 Learn more from the U.S. Department of Energy guide on air conditioner maintenance.

🌦️ Seasonal Maintenance Checklist

🌸 Spring: Pre-Cooling Season Prep

• Remove and clean the filter

• Vacuum inside the unit

• Clean coils and check for blockages

• Seal wall gaps or cracks with foam

• Test the thermostat and fan speed

☀️ Summer: High-Demand Usage

• Check filter every 2–3 weeks

• Watch for excessive condensation

• Monitor strange noises or vibrations

• Clean drain pan and inspect for clogs

🍂 Fall: End-of-Summer Cleaning

• Clean or replace the filter

• Deep clean coils and casing

• Inspect wall sleeve insulation

• Ensure proper drainage for any heat mode use

❄️ Winter: Cold Weather Shutdown or Heat Use

If you’re not using the unit for heat:

• Remove and clean the filter

• Shut off power to the unit

• Cover the exterior vent with a weather-resistant shield

If your unit also provides electric heat or heat pump functions, keep the filter and coil maintenance going — and inspect the heat strip or compressor as recommended by your manual.

💧 Drain Lines & Condensate Management

Through-the-wall ACs usually include a drain hole or drip tray. If this becomes clogged, water can back up and damage walls or flooring.

🧽 How to Clean the Drain

• Locate the drain hole at the bottom rear of the unit

• Use a pipe cleaner, compressed air, or vinegar solution to clear it

• Wipe out any built-up algae or sludge from the pan

🧊 Dealing With Ice Buildup

If your unit starts to freeze over, it’s usually due to:

• Dirty filter

• Blocked evaporator coil

• Low refrigerant (requires a pro)

Unplug the unit, let the ice melt, and check all airflow paths before calling for service.

🧰 Tools You Should Have on Hand

💡 Bonus Efficiency Hacks

• Use a programmable thermostat to reduce unnecessary runtime

• Seal leaks around the wall sleeve with foam or caulk

• Close drapes during hot afternoons to reduce heat gain

• Clean the area outside the unit to allow airflow

According to the Energy Efficiency and Renewable Energy (EERE) office, these small actions can result in up to 20% energy savings annually.

📋 When to Call a Pro

While most TTW AC maintenance is DIY-friendly, call a certified technician if:

• The unit leaks refrigerant or smells of burning

• You hear grinding or screeching sounds

• It fails to heat or cool even after basic upkeep

• There's mold growth inside the unit or ducts

A yearly tune-up is a good idea before the cooling season begins — especially for units used for both heating and cooling.

🛡️ Final Thoughts: Protecting Your Investment

Maintaining your through-the-wall AC doesn’t just preserve comfort — it extends the life of your system by several years. With just an hour or two each season, you can keep your unit running quietly, efficiently, and cleanly.

In the next topic we will know more about: Troubleshooting Guide: What to Do If Your Wall AC Isn’t Cooling (or Heating)