How to Clean a Moldy Window Air Conditioner
Deep clean and remove mold from a window AC unit by removing the outer casing, protecting the electronics, and flushing the coils and blower wheel.
- Read the tools, materials, safety notes, and steps below for free.
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🧰 Required Tools & Equipment
- ✓ Phillips screwdriver
- ✓ Garden hose with adjustable spray nozzle
- ✓ Soft-bristle nylon brush
- ✓ Fin comb or plastic putty knife
- ✓ Microfiber towels
- ✓ Wet/dry shop vacuum
📦 Materials & Supplies
- ✓ No-rinse foaming coil cleaner
- ✓ Plastic trash bags
- ✓ Painter's tape
- ✓ Mild dish soap
⚠️ Safety Checkpoints & Warnings
- • Ensure power cord is fully disconnected from the wall outlet before touching any screws or wiring.
- • Completely wrap and tape plastic around the electronic control board and fan motor before introducing any water.
- • Wear eye protection and nitrile gloves when applying chemical coil cleaners to prevent skin and eye irritation.
📋 Step-by-Step Guide (7 Steps)
Unplug and Move Unit Outdoors
Disconnect the power cord from the wall outlet completely. Carefully lift the air conditioner out of the window frame and transport it to an outdoor workspace such as a sturdy patio table, sawhorses, or driveway.
- • Unit is resting flat on an outdoor elevated surface with power cord clearly unplugged and wrapped.
- • Attempting to deep clean the unit while it is still mounted in the window frame.
Remove Front Grille, Filter, and Outer Metal Casing
Pop off the front plastic faceplate and remove the mesh filter. Use a Phillips screwdriver to extract all perimeter screws securing the top and sides of the sheet metal case, then slide the case backward and off the chassis.
- • Outer metal cover is fully detached, exposing the internal aluminum coils, fan motor, and base pan.
- • Forcing the metal case off without removing hidden lower side or rear screws.
Waterproof the Electrical Control Box and Motor
Locate the plastic-encased control board and the center fan motor. Wrap thick plastic trash bags tightly around the entire control panel assembly, capacitor, and motor housing, sealing every edge with painter's tape.
- • Control board box and electric motor are completely sealed under taped, waterproof plastic.
- • Leaving small gaps in tape around wiring bundles where water can seep into the control board.
Dry-Brush and Vacuum Loose Debris
Use a soft-bristle nylon brush and a shop vac to remove loose dirt, leaves, pet hair, and surface mold from the evaporator and condenser coils. Gently brush in a strict vertical direction parallel to the aluminum fins to avoid bending them.
- • Coil surfaces are free of heavy lint blankets and visible dirt buildup in the lower tray has been vacuumed.
- • Brushing horizontally across the aluminum fins, which crushes them flat and blocks airflow.
Apply Foaming Coil Cleaner to Coils and Blower Wheel
Shake the foaming coil cleaner vigorously and spray it liberally across the front evaporator coils, rear condenser coils, drain pan, and inside the cylindrical blower fan. Allow the foam to penetrate for 10 to 15 minutes to break down mold, mildew, and stuck grime.
- • Thick white foam covers all coil surfaces, blower blades, and bottom tray surfaces uniformly.
- • Wiping the foam off immediately without letting the chemical dwell and dissolve mold.
Rinse Coils and Flush Base Pan
Set the garden hose nozzle to a gentle shower or low-pressure spray pattern. Rinse the coils thoroughly from top to bottom and flush dirty runoff out through the rear base pan drain holes, aiming water strictly away from covered electronics.
- • Water running out of the base pan drain hole runs clear, and aluminum coil passages are clean and visible.
- • Using a high-pressure jet stream that flattens fragile aluminum fins immediately.
Dry, Remove Plastic, and Reassemble
Remove the protective plastic and tape from electrical areas, inspect them to confirm they are 100% dry, and towel-dry the chassis base. Allow the unit to air dry in the sun for at least 2 hours before sliding the metal case back on, screwing it tight, and reinstalling the clean filter and front grille.
- • Unit is fully reassembled with metal casing flush, all screws tight, and clean front grille in place.
- • Plugging the unit in immediately while internal moisture remains near motor shafts or wiring.
Credit: inspired by an original tutorial by The Fixer — watch the original on YouTube.
Don’t have everything?
- No No-rinse foaming coil cleaner? Spray bottle filled with warm water and 2 tablespoons of mild dish soap
- No Fin comb? Old plastic gift card or dull plastic putty knife