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Air Conditioner Smells Bad When Turned On: What’s Causing It?

air conditioner smells bad when turned on

An air conditioner is a must-have during Florida’s summer months, and most people use theirs around the clock. If your air conditioner smells bad when turned on, it’s a major inconvenience. But does it need immediate attention?

What causes bad smells in air conditioning systems? As a leading choice for AC repair in Cooper City, Florida, Cool by Design has seen it all. 

Below, we share why you may have an unpleasant smell coming from your air conditioning unit and what to do about it.

Possible Causes of Bad Smells in Your Air Conditioner

A Mold and Mildew Smell

Do you perceive the unmistakable musty smell of mold and mildew coming from your air conditioning unit? Don’t ignore it; it’s one of the top signs of dirty air filters or coils.

The filters in your air conditioning unit are there to keep out airborne contaminants. If you don’t replace them, the filters become the perfect breeding ground for mold, mildew, and other pesky organisms. Every time you turn on the air conditioner, the unit will spread spores into your space.

If the problem lies in the evaporator and condenser coils, quick solutions could save the system a lot of trouble. Coils play an integral role in the cooling process because of the refrigerant coursing through them. However, dirt, debris, and excessive moisture on the coils can encourage the growth of mold and mildew, which reduces their functionality and spreads quickly.

Additionally, dirty air filters and coils don’t just cause bad smells—they can cause a host of other problems. It’s best to regularly replace your filters and keep the coils spotless.

A Smell of Decay

If your air conditioner smells bad when turned on, and it smells like there’s a dead rodent in there, you’re probably right! Decay is distinct and hard to miss, whether it’s birds, lizards, or rodents that have died in air ducts or inside the indoor unit.

If you get hit by that terrible smell as the cold air comes through your vents, you have two choices: 

  1. Call a technician right away to clean your duct and your air conditioner.
  2. Live with the doors and windows open and your air conditioner running for a few weeks and wait for the dead critter to finish decomposing.

That second option will drive up your energy bill for a few days or weeks. However, it’s not a great idea if the dead critter is inside your indoor unit, as this could damage the components in the system. If you leave it to play out, you might find yourself paying for a replacement unit on top of higher utility bills.

The Smell of Dirty Socks

Does your air conditioner smell like wet socks? You may have clogged drain lines or stagnant water in your drain pan. In both cases, your air conditioner will create a conducive environment for mold, mildew, bacteria, and algae, so it’s best to clean these out as soon as possible.

  • Clean out the drain line with a dipstick.
  • Throw out stagnant water in your drain pan or mop it up with a wet/dry vacuum cleaner. 
  • Clean the pan with a bleach or vinegar solution to stop the growth of any microorganisms.

Unfortunately, dealing with the standing water and unclogging the drain line doesn’t address why you have standing water in the first place. It’s best to call in a professional to thoroughly inspect your unit and diagnose the problem.

A Burning Smell

Does your air conditioner emit a burning smell as the cool air starts to come through? You may have burning electrical components inside your unit. 

Shut down the air conditioner to a house fire! If you smelt it within the first few days after turning on the air conditioner after months of using only the heating system, it could just be burning off dust. However, it’s safer to have a professional check out the system.

A Chemical Smell

Does it smell like chemical fumes when your air conditioner works? You’re probably dealing with a refrigerant leak, which means that your unit isn’t absorbing heat as it should and that you have a toxic substance leaking into your space. To avoid refrigerant poisoning, turn off your air conditioner and call an HVAC technician.

Improve Your Home's Air Quality With Cool By Design Today!

If your air conditioner smells bad when turned on, catching underlying problems requires professional attention. Cool by Design’s technicians can fix all the common causes of a bad-smelling air conditioner, from a refrigerant leak to dirty condenser coils.

Call Cool By Design at (954) 417-1580 today to learn more!