Why Does My Air Conditioner Smell Weird When I Turn It On?

By May 7, 2018 June 28th, 2024 Air Conditioning
Bad AC Smell

As the weather warms up, more people are using their air conditioner to keep their home cooler. To be sure, making sure your A/C unit is working well is essential, but there are possible problems it’s important to troubleshoot if you notice odd smells coming from the unit when it’s turned on for the first time.

What kind of odor is coming from your A/C unit? A number of causes may be the culprits, so being aware of what might be making the funny smell coming from your air conditioning system can help you determine how to make the smell go away.

Common A/C Unit Smells

Mildew Smell

A moldy smell coming from your air conditioner that reminds you of a wet towel smell may signify mildew, mold, or fungus growing inside of or on the outside of the A/C unit. One of the reasons your air conditioning system’s mildew smell might be occurring is because the compressor might not be draining properly, so the moisture lingers and causes the smell. In addition to the compressor draining poorly, your A/C might need its filters cleaned or replaced.

Rotten Egg Smell

If your A/C unit smells of rotten eggs or rotten garbage, there is a good chance an animal may have gotten into the unit or HVAC system and died. It is likely this happened during the winter when your A/C unit was not in use. If you notice this smell coming from your unit, do not try to clean out the dead carcass yourself. Many dead animals may have diseases or other health hazards to humans, making removing them possibly damaging to your health. Instead, contact an experience HVAC technician for their help with your problem.

Sewage Smell

Like with a rotten egg smell, a sewage smell coming from your air conditioner can indicate a hazardous cause. If you smell sewage when you turn on your A/C unit, your sewer system may have backed up into your house or near your unit, and the smell may come from a ruptured pipe.

Contact an air conditioning company right away if you notice a sewage smell or detect methane in your home. Do not let this problem linger!

Gunpowder or Electrical Smell

Many older homes experience electrical problems, so it’s no surprise that a home with an older A/C unit might cause a smell like burning gunpowder or an electrical smell when they are turned on. One possible way to resolve a gunpowder smell coming from an air conditioner include replacing a blower fan that has burned out in the unit. Additionally, a shorted circuit board may cause a gunpowder smell to come from an air conditioning system that has been turned on after a long time of disuse.

Gas Smell

When you turn on your A/C unit for the first time and smell gas burning, the cause may either be normal or a major cause of concern. For one thing, dust settling in the heat exchanger HVAC system can smell like gas burning off. However, the location of the smell is critical to know to determine whether or not you have a major problem that could require help.

If you notice the gas smell coming from the vents, dust is the likely culprit. Nonetheless, if the smell is not coming from your HVAC system vents, you might have a pipe fitting leak or a leak within the equipment of your A/C unit. Contact an experienced technician to help you determine the leak source and repair it, or if they identify a gas leak, other parties might have to be involved right away such as your gas company.

Oil Smell

An oily smell coming from your air conditioner may result from an oil leak at the unit. The presence of oil will also indicate a leak, so look for both the oil and the smell when troubleshooting this problem. A technician can tighten the fittings on the unit to ensure the leak stops, and the areas they might tighten fittings on include at the tank, the oil line, or the filter.

An additional cause of the oil smell coming from an A/C unit might be from a malfunctioning oil burner. There are usually other signs of a problem when this oil smell comes out of your unit, such as a burner that has become clogged of a fuel pump in need of replacement. There may also be unusual sounds coming from the unit, which could signify other problems. Only a trained HVAC technician can truly determine the cause of an oil smell coming from an air conditioner.

Stinky Feet Smell

No one wants a bad smell to spread throughout their home, so when a smell similar to stinky feet comes out of an A/C unit, you’ll want to identify and fix the problem right away! Like with a mildew smell coming from your unit, a stinky feet smell might indicate standing water that has not drained correctly in a unit. A technician can come check your unit for a drainage problem if you notice this smell coming through your vents.

Old Cigarette Smell

Homes where smokers lived or have lived in the past (in the case where a new homeowner begins to occupy a home) may experience an old cigarette smell coming from an air conditioner if it has been off for some time. The evaporator coil on the system may be emitting this smell, and having a trained technician experienced in A/C maintenance check your unit and clean the coil will fix the problem.

Other A/C Problems to Monitor

In addition to funny smells coming from your air conditioning system, any homeowners may notice other problems. Common A/C problems to watch for that might be of concern include:

  • Water leaking from indoor unit
  • Puddles of water
  • Frozen coil
  • Outside fan not working
  • Unit blowing warm air

Contact an HVAC Technician

If any weird smells or the above problems develop in your air conditioning system, an experienced AC service technician can diagnose and repair your problem. Design Aire can assist homeowners in A/C maintenance and repair in the St. Louis and St. Charles areas. Contact us today to learn how we can help!