Dust gets deposited on the cooling fins…then becomes damp because air conditioners condense water out of the air. Damp dust is an excellent breeding ground for mold! Between cycles, and when the unit is not needed, that mold can have a real party.
These steps are for WINDOW units…sadly, Central air usually requires a professional. All you can do is check/clean the air filters and remove debris around your outside unit.
Cut the power off to your unit (unplug it or hit the breaker)
Remove and clean the air filter. Some you can wash and some you can NOT wash – check your users manual. If yours is like ours, it has to be vacuumed. If you can’t find your manual (it happens) do a quick Google search for one, they all seem to be online.
Next comes the removal of the front panel. Get out the bucket of bleach water and get busy with it. Clean the entire thing as mold could be there – but not visible to your eyes yet.
Now you clean the inside of the unit. Take that bleach water and get busy. Be careful not to get any of the electrical controls wet and watch for sharp edges. They do have professional foaming evaporator coil cleaner that you can spray on the indoor coil that foams up, cleans and then drains out like the condensed water. It’s more expensive than a bucket of bleach water and harder to find.