How to Clean Rust From Central Air Conditioner Coils

The condenser and evaporator coils are the very heart and most vulnerable parts of any central air conditioning unit.

Cleaning the Evaporator Coils

Rust will corrode the coils and risk ruining the entire system if not kept under control. The most direct way to avoid rust and unnecessary replacement costs is to clean them twice a year. The condensers are notorious for clogging up with dirt, weeds and pollen. Visible amounts of dirt, debris or rust signals that it is time to clean the coils. A couple hours of cleaning will save thousands in repairs or replacement.

Step 1

Shut off the air conditioning unit before cleaning the coils. It is best to shut the electricity off at the breaker box.

Step 2

Take off the cover over the evaporator coils by removing the screws holding it onto the unit. Set the screws aside so they will not be lost.

Step 3

Spray on an even layer of rinse-free coil cleaner, which you can purchase at most home improvement centers. Allow the cleaner to sit on the coils for 5 to 10 minutes.

Step 4

Wipe the surface of the coils with a soft absorbent cloth. Replace the cover and secure with the screws using a screwdriver.

Cleaning the Condenser Coils

Step 1

Remove the metal housing for the condenser coils. Generally, you must remove a number of screws along the bottom edge that hold the cover in place. Each unit is a little different; consult the owner's manual for removal on your particular make and model.

Step 2

Rinse the coils with a medium-strength stream of clear water from a garden hose. Keep the water stream pointing straight at the coils so as not to damage them.

Step 3

Spray on a layer of the coil cleaner. Allow another 5 or 10 minutes for the product to sit on the condenser coils before rinsing with clear water.

Step 4

Replace the metal housing.

Step 5

Turn the electricity back on to the air conditioning unit.

Things You Will Need

  • Safety glasses
  • Gloves
  • Screwdriver
  • Rinse-free coil cleaner
  • Absorbent cloth
  • Garden hose


  • Pouring a bucket of water slowly over the coils is a safer alternative if you have inordinately high water pressure. Too much force on the fins will bend or break them.


  • Wear safety glasses and gloves when working with chemical coil cleaners.