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Why Does My AC Smell Like Vinegar?

air that smells like vinegar blowing through a home

Is there anything better than the fresh cool breeze of an air conditioner on a sweltering summer day? No way.

However, if your AC smells like rotten eggs or vinegar, that pleasant respite from the heat is going to sour. Air conditioners that emit an unpleasant smell are not only a buzzkill to your refreshment and comfort, they are also warning signs of serious functional issues and potentially expensive breakdowns.

In short, that bad smell is your AC’s way of letting you know that something is wrong and needs to be fixed. An off-putting vinegar odor is most typically caused by a build-up of bacteria or mold in your AC system. This can continue to grow and spread throughout your home.

The good news is that this is a fairly common issue and there are some tried-and-true methods to resolve it.

The first step in dealing with a sour-smelling air conditioner is to determine what is causing that vinegar-like smell in the first place. Once the cause has been discovered, steps can be taken to remedy the situation.

A few things that can cause your air conditioner to smell bad include the following.

Excess Condensation

The temperature of the air emitted by your AC is controlled by cooling coils. Fans pull air into the system and pass over these cold coils. These coils cool the air before blowing it back out into the house.

Like warm air passing over a cold glass, this process causes condensation, the formulation of small water droplets. By design, this moisture collects into a drip pan (commonly called a “condensation pan”). This moisture is then automatically or manually drained from the system.

However, when there’s excess condensation or a failure in the drainage process, the build-up of moisture can invite the growth of molds or fungus. This can produce an unpleasant smell and can hinder the system’s effectiveness. Eventually, this can lead to malfunctions or costly damages.

Clogged Air Filter

The air filter’s job is to filter contaminants from the air coming into the system. Then, prevent them from blowing back out with the cooled air. If the filter becomes clogged from overuse, or wet from excess condensation (or both), mold and fungus can grow on the filter.

The air passing through the system not only picks up the smell of this contamination but can spread its spores and toxins throughout your home.

Full or Clogged Condensation Pan

A condensation pan can also be the culprit of a sour, vinegar-like odor. Older air conditioning units may have issues with buildup in the condensation pan that can cause blockages in the AC drain line. This, in turn, can transform your condensation pan into a stagnant bog, and a breeding ground for all kinds of nasty stuff. Stuff that not only smells bad but can pose a serious health threat.

an air conditioning vent

Mold in the AC Unit

Of all the growths and toxins that can infest a poorly functioning AC system, mold is the most common threat.

Molds ingest dirt and dust that are pulled from the incoming air, and will coat the interior surfaces of a unit that isn’t cleaned properly, or often enough. Once mold has established a colony, especially in an out of the way or hard to reach area, it can be very difficult to get rid of, and poses a serious health threat.

Some physical symptoms that can occur in people who are breathing mold-infested air can include:

  • Frequent headaches
  • Coughing, sneezing and other allergy-like symptoms
  • Nasal or sinus congestion
  • Difficulty breathing and sleeping
  • Frequent and unexplained fatigue

If you or other members of your household suffer from any combination of these symptoms, especially if the symptoms seem to disappear once they’re out of the house, it could be a sign of a mold problem and you should take immediate action.

Those are some of the reasons why your house and/or AC output is smelling funky.

Now, let’s take a look at some simple steps that you can take to resolve these issues and start enjoying your AC again.

If you don’t have the time, physical ability or even just the inclination to try these steps yourself, you can skip them and go right to contacting a professional who specializes in AC services.

Clean or Change Air Filter

This is the simplest, quickest, cheapest and often most effective way of dealing with a stinky AC unit. It’s also the first fix you should try. This seemingly small fix can prevent other large issues, such as your AC not turning on. Unfortunately, it’s also one of those “honey-do” jobs that many homeowners put off for long periods of time.

Not only can a clean filter resolve odor issues, but it also allows your system to run more efficiently, which means cleaner, cooler air at lower energy costs.

Most manufacturers recommend using high-quality air filters and replacing them quarterly (every three months). If you have a lot of people and/or pets, in your home, or live in an area with frequent air-quality issues, you may need to do so more often.

If you can’t remember the last time you replaced your air conditioner’s air filter, it probably means it’s time to put a new filter in your unit.

Minimize Moisture

If your condensation pan requires manual emptying or cleaning, do it regularly and often, especially in the high-use summer months. Removing stagnant water from the system can be a major factor in inhibiting mold creation and growth.

If your pan drains automatically, make sure to check it periodically to ensure that it’s draining properly and there are no plugs or leaks.

If there are, or if it seems that excess condensation is overwhelming your drip pan, or there’s an excessive build-up of moisture, puddles or signs of water damage elsewhere in your AC system, contact a professional to avoid any further damage to your air conditioner or home.

Clean Your Vents

Cleaning your AC vents is another easy, low-tech, but important step in maintaining a healthy air conditioning system. A good brush, some anti-bacterial cleaner and a handful of paper towels will typically get the job done.

If you want to go the extra mile (or inches, in this case) remove the vent panels and, using a hose attachment, vacuum the dust and debris from air shafts, as far as you can reach, as well.
If that smelly air has been blowing through the system for a while, it’s likely to have absorbed into any dirt or dust coating the ventilation system, too.

a clogged ac drain line

Unclogging an AC Drain Line

Again, dirt, dust and other airborne contaminants can collect over time and accumulate to plug up your drainage lines. Even if lines don’t become completely plugged, restrictions in water flow can cause excess condensation and reduced performance.

Unclogging your AC drain line is a technical task. Most homeowners should contact a licensed professional for this AC service. However, if you are handy, you can follow these steps to check and unclog your AC drain lines:

  • Power off the air conditioner, and turn off the power flow to the room it’s in (typically from a breaker box).
  • Check the drain pan. If there’s moisture built up, dump the pan or empty it with a shop vac or dry rags.
  • Remove any visible build-up from the drain opening and use suction (shop vac) or water pressure (a hose) to unclog the drain line.
  • Once clear, clean out the line with a commercial PVC cleaner and then flush with clean water.
  • Once the line is cleaned and rinsed, reassemble and reinstall all of the components, turn the power back on, and turn on the AC system to test that everything is working and the odor is gone.

These steps may require some technical know-how, physical flexibility or even specialized tools or instructions. Always refer to your manufacturer’s specific instructions (and warranty limitations) before working on your AC, or contact a licensed professional to do the job for you.

If the AC smell remains after changing the filters, cleaning the vents, draining the condensation pan, and unplugging and cleaning the system, it means that the molds or other contaminants are located deeper within the system than you’re likely going to be able to reach, and it’s definitely time to contact the HVAC pros. Similarly, if your AC drain line keeps clogging, you should contact a pro instead of trying to do it yourself.

Let’s face it, life’s too short to live with a stinky air conditioner.

Keep your system clean with regularly scheduled AC maintenance and high-quality filters, and enjoy your home in the cool (and odorless) comfort that you deserve!

ABC Can Maintain Your AC System

One of the best ways to keep your AC system in tip top shape is to sign up for regular maintenance. If you’re looking for a professional to perform that maintenance, contact ABC Home & Commercial Services. We can ensure that your system is working as it should and we will catch any needed AC repairs early.

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