How to Clean a Window AC Unit: A Simple Homeowner’s Guide

Window air conditioners are a great solution for cooling smaller spaces and helping you stay comfortable throughout Minnesota’s warm months. However, like any cooling system, they require regular cleaning to function efficiently. Dust, dirt, mold, and debris can build up inside a window AC, reducing airflow, increasing energy use, and even affecting your indoor air quality.

At MD’s Heating and Air Services, a family-owned HVAC company serving the Twin Cities, we know that proper care—paired with routine AC maintenance—keeps your cooling systems running longer and more efficiently. This guide walks you through the step-by-step process of cleaning a window AC unit and explains when it’s time to call in a professional for AC repair or a more permanent cooling solution, such as AC installation.

Why Cleaning Your Window AC Matters

A clean AC runs better—plain and simple. Dirt buildup forces your system to work harder, which:

  • Raises your electric bill
  • Reduces cooling performance
  • Creates unpleasant odors
  • Can lead to mold or mildew growth
  • Shortens the lifespan of your unit

Regular cleaning helps you avoid unnecessary repairs and keeps your home more comfortable during the hottest days of heating and cooling in MN.

What You’ll Need

Before getting started, gather these supplies:

  • Screwdriver
  • Soft cloths or microfiber towels
  • Mild dish soap
  • Warm water
  • Vacuum with a brush attachment
  • Fin comb (optional)
  • Spray bottle
  • Protective gloves
  • Soft brush or old toothbrush

Step 1: Unplug and Remove the AC Safely

Always unplug your window AC before cleaning. If possible, remove the unit from the window and place it in a stable area, such as a porch, garage, or bathtub. This makes cleaning easier and safer.

If your AC is too large or heavy, you can clean the major components while it remains in the window—just be extra cautious.

Step 2: Remove and Clean the Air Filter

The air filter is one of the most important components to clean regularly. Most window AC filters are reusable.

  1. Slide or pop the filter out from the front panel.
  2. Rinse it under warm, running water.
  3. Use mild soap if needed for stuck-on dirt.
  4. Let it dry completely before reinstalling.

Dirty filters can reduce airflow and strain your system, which may eventually require AC repair if ignored. Replace the filter if it’s damaged or worn out.

Step 3: Vacuum the Interior Components

With the front panel off and the filter removed, use a vacuum with a soft brush attachment to remove dust from:

  • The evaporator coils
  • The fan
  • The interior casing

This helps improve airflow and keeps your AC running smoothly. Be gentle—these components can be delicate.

Step 4: Clean the Coils

Your AC has two sets of coils:

  • Evaporator coils (inside)
  • Condenser coils (back/outside)

Mix warm water with a bit of mild dish soap and spray the coils. Let the solution sit for a few minutes, then wipe it with a soft cloth.

For tougher buildup, a specialty foaming coil cleaner (available at hardware stores) can help. Straighten any bent fins carefully using a fin comb to support optimal airflow.

Dirty coils often lead to reduced cooling and higher energy bills—one of the most common concerns homeowners bring up during HVAC maintenance visits.

Step 5: Clean the Drainage System

Window AC units remove moisture from the air, and this water must drain properly. Over time, the drainage channel can clog.

  • Inspect the drain hole at the bottom of the unit.
  • Remove debris or buildup with a toothpick or brush.
  • Ensure water flows freely to prevent leaks or mold.

If your unit leaks frequently, it may indicate a larger issue that requires professional AC repair.

Step 6: Wipe Down the Exterior

Finish by cleaning the outer casing and front grille. Use mild soap and a damp cloth to remove dirt and dust.

Let all components dry completely before plugging the AC back in.

When to Call a Professional HVAC Technician

Even with regular cleaning, window ACs have limits. You should contact a professional if your AC:

  • Still blows warm air
  • Makes unusual sounds
  • Emits moldy or burning odors
  • Has weak airflow
  • Leaks water repeatedly
  • Freezes up frequently

In many cases, it’s more cost-effective to upgrade to a whole-home cooling system. MD’s Heating and Air Services offers expert AC installation and comprehensive HVAC installation services designed to enhance energy efficiency and long-term comfort—especially crucial for homeowners relying on Minnesota heating and air conditioning year-round.

Trust the Twin Cities' Local HVAC Experts

Cleaning your window AC is a great way to keep your home cool and your energy bills low. But when deeper issues arise, trust MD’s Heating and Air Services—your local family-owned HVAC company—for reliable AC repair, seasonal AC maintenance, and high-quality HVAC installation.

Whether you’re battling summer heat or gearing up for winter, we’re committed to keeping your home comfortable all year long.