Sears Knowledge Center

How to Fix a Smelly Air Conditioner

Summer is supposed to smell good, right? Freshly mown grass, suntan oil, flowers blooming and burgers on the grill make summer a happy time of year for our olfactory glands. The last thing we want ruining this brief paradise is a smelly air conditioner that reminds us less of today's picnic on the beach and more of last week's leftover poached fish. If your air conditioner has developed a stench, don't resort to turning it off and broiling in your home. Get to the root of the problem yourself by following these steps.

What you'll need:

  • Fin comb. This will straighten bent coil fins.
  • Bleach and water mixture. One part bleach and three parts water will help you clean any mold or mildew.
  • Coil cleaner. This will clean conditioner coils if you have mold.
  • New filter. You may need to replace your filter, so always have one on hand.

Step 1: Cut power to the unit. As with all repairs, safety should come first.


Step 2: Change or clean the filter if needed. Filters should be changed every 30-60 days, depending on if you have pets, allergies or a naturally damp home. Clean the filter by removing the mesh filter and front grill of the unit and washing them with warm water and a little bleach to kill odor-causing bacteria.


Step 3: Clean mold and mildew build-up. If you spot mold or mildew, clean the evaporator coils behind the filter and condenser coils at the back with a coil cleaner. If the coil fins are a little bent up, an inexpensive fin comb will straighten them out and help to prevent future build-up. Remove the condensation drain line and flush it with the bleach solution. Wash the drip tray with hot, soapy water and bleach and make sure that everything is clean and dry before turning the unit back on.


Step 4: Check your drain. If the drainage system gets clogged with dirt particles, water builds up in the drip tray. In humid climates or when the unit is running extensively, the water doesn't evaporate and begins to grow foul-smelling bacteria and mold. Clear the drainage holes and clean and disinfect the tray (and coils if they are affected, too).


Step 5: Run the air on high. If your unit is running on a low setting for an extended period of time, the air may not be dehumidifying enough to prevent mold growth. After you've gone through all the steps to clean it, be sure you're running the unit on high occasionally to prevent mold growth.


Step 6: Call a HVAC expert. If everything else fails, call a professional. Your smelly air conditioner may be due to the unit being oversized for the area it's serving. Mold can easily grow in a unit that isn't able to work at full capacity.

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