Why is my AC blowing smelly air?

Author: Ms. Kaylin Hill  |  Last update: Monday, March 31, 2025

After a long period of time without use, mold and bacteria can build up on your evaporator coil or other areas of your air conditioner's HVAC system. Your air filters are your first line of defense against mold and bacteria build-up. If the smell doesn't go away, you should first clean or replace your filters.

How do I get rid of the smell in my air conditioner?

To make your air conditioner stop smelling bad, clean or replace the air filters, ensure the condensate drain is unclogged, and clean the evaporator coils. Check for mold or mildew inside the unit and use a disinfectant spray designed for AC systems. Regular maintenance helps prevent odors from developing.

How do you fix smelly air vents?

Remove excess dust using a clean, dry dusting cloth. If you can't see anything shining through after cleaning, buy new filters and replace them. Test the system by running it to see if it's functioning correctly and if the musty smell is gone. If the smell persists, contact a professional for help.

Should I turn my AC off if it smells?

It's because the a/c collects water from the air while running and creates condensation on the coil and compressor. So by shutting off the air conditioner and just letting the air blow with ac off it dries it up and prevents water from sitting around and becoming stinky/moldy.

Why does my house smell like sewage when the air conditioner runs?

Clogged Drain Line: AC units have a condensate drain line that removes excess moisture. If this line is clogged, water can back up and create a musty smell that resembles sewage.

How to deal with a smelly air conditioner.

Why does my AC vent smell like poop?

The smell of raw sewage coming from an AC vent is never a good sign. It usually indicates a backed-up sewer line or ruptured sewer vent pipe somewhere near the ductwork. All it takes is a bit of methane from the backup to fill your house with a nasty smell.

How to tell if a p-trap is dry?

Identifying a Dry P-Trap

Here are the signs to look out for: Persistent sewer gas odours near sinks or floor drains. Drains that gurgle or make unusual sounds. Infrequently used fixtures, such as guest bathrooms or utility sinks, are familiar places for dry P-traps.

Why does my AC stink when it blows?

Evaporator coils remove heat from the air, so they are a vital part of any air conditioning unit. However, over time mould can accumulate on and around evaporator coils, resulting in a mouldy smell coming from your air conditioner.

How to clean a condensate drain line?

How to Clean Air Conditioner Drain Line With Vinegar in 6 Steps | Drain Line Cleaning
  1. Turn off your air conditioner. ...
  2. Locate your condensate drain line. ...
  3. Identify the access point on the drain line. ...
  4. Flush with distilled vinegar. ...
  5. Let the solution sit for 30 minutes. ...
  6. Repeat each month.

What is dirty sock syndrome?

“Dirty Sock Syndrome” refers to when a foul-smelling, mold- or mildew-like odor comes from your air conditioner when you first turn it on. This happens when moisture, dust, and dirt build up on your AC system's evaporator coil, inviting bacteria and mold to multiply.

What can I put in my AC vents to smell good?

If you are wondering what to put in the bags, consider lavender blossoms, cloves, sandalwood paste, or rose blossoms. Try mixing up scents until you have something that appeals to you. Your AC unit can help disperse revitalizing lemons scents around the house.

How often should air ducts be cleaned?

Experts advise having your air ducts cleaned every 2 to 3 years to prevent many maintenance and health problems before they start. However, homes with pets or children with allergies should have their air ducts professionally cleaned more frequently than the recommended average.

What does mold in AC smell like?

The distinctive earthy smell emits a pungent odor that resembles old books or wet dirt. Other than the musty smell from A/C systems, other common odors to look out for that indicate issues include: Burning: A burning smell or gunpowder odor indicates an electrical or mechanical problem.

What are the symptoms of mold in the air ducts?

Symptoms of Mold in Your Air Ducts
  • Dank odor when the HVAC system is on.
  • Presence of visible mold on the air vents and grilles.
  • Irritation of the respiratory system such as the lungs, nose, and throat.
  • Sneezing and watery eyes.
  • Fever, insomnia, nausea, and headache.

Why does AC smell when the compressor is off?

Sudden increase in humidity. The coil gets wet from condensation but when the compressor is running the air is cold so it's ability to absorb water is very low. When the compressor turns off the air heats back up, absorbs the water from the coil and blows the humid air out of the vents.

How do I know if my AC drain line is clogged?

A clogged AC drain line symptoms include:
  1. Musty, moldy smell near your indoor unit or in air from the registers/vents.
  2. Standing water near the indoor unit.
  3. Water damage in areas near the indoor unit.
  4. AC system is not cooling your home.
  5. AC system shuts down or doesn't turn on.

What is the best way to unblock a condensate pipe?

Locate the white plastic pipe that leads outside, then check for any blockages like debris or ice. Defrost ice with warm water, not boiling, and use a rod or wire to push through the obstruction. If that doesn't work, call a pro with specialist equipment.

How often should I put vinegar in the AC?

Repeating the vinegar cleaning process once every month will keep your AC drain line in great condition. The cleaning process is exceptionally effective at removing unwanted bacteria and fungi, allowing your AC to run efficiently. Call (702) 944-8838 Today or Book Online for Heating and Cooling Service!

How to fix a smelly air conditioner?

If your AC smells musty, empty your drain pan or check your drain line for clogs. Next, check your air filter for signs of mold and change it if necessary. Clean off your evaporator coil, keeping it clear of dirt, bacteria, and other grime.

How to clean an AC drain line?

Different Ways to Unclog Drain Lines in Your AC
  1. Plunger Method. ...
  2. Use a Wet/Dry Vacuum. ...
  3. Pour One Cup of Vinegar Down the Drain Line. ...
  4. Pour One Cup of Bleach Down the Drain Line. ...
  5. Blow Air Through the Line. ...
  6. Flush Clean Water Through It. ...
  7. Use Chemical Drain Cleaners. ...
  8. Use an Electric Snake.

Why does the air coming out of my AC vents stink?

HVAC systems use filters to remove fine particulates from the air. Over time, the impurities taken out of the air accumulate on an air filter, reducing airflow. When this happens, the material caught in the vent may start to decay and give off odors.

How do you fix a smelly P-trap?

To eliminate odors coming from a dry p-trap, pour half a gallon of water into the trap to restore the barrier. It will prevent the odors from seeping through the drain. Another helpful method is to add a cup of white vinegar bleach to get rid of larvae and slow down the evaporation.

How do I know if my P-trap is clogged?

A blocked p-trap will cause water backflow to occur. The first sign that your p-trap is clogged is when the water in your sink takes longer than average to flow down the sink.

How do you clean a P-trap without removing it?

Pour some baking soda down your drain and then pour boiling water down after. Sometimes this will clear the clog. Use a plunger on your sink drain to try to force the clog out of the trap.

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