Step 1
Look for the filter in the blower compartment of the furnace. It will be in an attached filter case or in a return air grille in a wall of the house.
Step 2
Turn the air conditioner off at the circuit breaker.
Step 3
Remove the filter. It will most likely slide out. There will be a tab to pull or a couple of screws to remove.
Step 4
Vacuum the filter. You can also wash it, which is good for removing bacteria as well as dust. Allow the filter to dry thoroughly and replace it. If the filter is absolutely filthy, replace it. Look for tears and replace the filter if there are any.
Step 5
Clean the coils. Remove any casing and simply look for fins and copper pipes—they are the coils. There will be at least one outside in the condenser and at least one inside. Blow compressed air across the coils and brush clean. Use mild detergent and rinse for heavier soils. Use a pressure washer with special coil cleaner for heavy deposits. Be careful you don’t damage the fins. Pressure clean in the opposite direction of air flow through the coil.
Step 6
Allow to dry and turn the air conditioner back on.