Just because you’ve shut down your air conditioner for the heating season doesn’t necessarily mean it’s out of sight and out of mind. If you’re like a lot of homeowners, your A/C may give off foul odors year-round. That’s why it’s important to know how to prevent smelly A/C systems.
What Causes a Smelly A/C System?
Over time, the indoor unit of your home’s split-system A/C can collect mold, bacteria and other bad smelling substances, 
especially on the evaporator coil and condensate drain and pan. Your air filter can also accumulate foul-smelling contaminants. The typically dank, dark location of your indoor A/C unit exacerbates the smell, which may eventually circulate throughout your home, while your HVAC system is running.
Unfortunately, if you have a smelly A/C system, the problem may not just be foul odors. If your evaporator coil is coated with mold and grime, it can’t efficiently exchange heat between the air and refrigerant running through the coil. This means your A/C has to work harder to condition your home, which wastes energy and stresses the system.
How to Clean a Smelly A/C System
Your A/C needs regular cleaning, either by the homeowner or a professional HVAC technician during annual maintenance. If you feel up to the job, first turn off your A/C’s power at the breaker box. Then, open the cover of the evaporator coil, which is typically located near the furnace or A/C air handler.
Once the unit is open, poke a stiff wire (perhaps a clothes hanger) into the condensate drain, to remove any accumulated dirt or debris. Then, clean out the drain pan, using a brush and rinsing with water. Next, wipe contaminants and dirt from the evaporator coil, using a clean, soft cloth, and then vacuum the coil with a wet/dry vac. Spray the coil with a special coil cleaner, following the instructions on the product. Lastly, remove the air filter and replace it with a new one.
For professional help cleaning your smelly A/C system, please contact Marsh Heating & Air Conditioning. We serve the Twin Cities area with professionalism and pride.
Our goal is to help educate our customers in Minneapolis-St. Paul, Minnesota about energy and home comfort issues (specific to HVAC systems). For more information about smelly A/C systems and other HVAC topics, download our free Home Comfort Resource guide.
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