Empty and clean the drain pan
If you have a mouldy smell coming from your air conditioner, the first thing to do is check your drain pan. If it's full, empty the water out, and it's also advisable to give it a quick clean with soap and water to remove any possible build-up of mould inside.
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.
This means that your AC is spreading dangerous mold spores into every room of your home. These spores can cause severe health issues, especially if one of your family members struggles with allergies. Homeowners should never ignore strange smells coming from their HVAC systems.
A burning, electrical odor or gunpowder-like smell could indicate electrical issues, fried circuit board, compressor, or fan motor problem. Prolonged exposure to these fumes is not healthy. And letting your system continue to run after you notice it could lead to some costly repairs.
Dust, hair, and moisture on the AC filter encourage mildew growth, which can cause a musty odor when the air conditioner runs. This is a likely reason why the air conditioner smells when first turned on if you don't use forced-air heating in winter. To help prevent this odor, clean or replace the filter in the spring.
It could be as simple as a dirty air filter or mold growth caused by excessive condensation in the HVAC unit or as bad as a freon leak or, even worse, a ruptured sewer vent pipe or a backed-up sewer line near some ductwork.
Your AC uses different fluids but none of them should cause a noticeable odor. The chemical smell could be coming from a freon leak or certain types of air filters. It's best to contact an HVAC expert to diagnose the source of the chemical smell.
You can prevent a clogged AC drain by performing routine cleaning. By pouring a ¼ cup of vinegar into your AC's drain line, you will kill any mold, algae, mildew, and other forms of bacteria or fungi, preventing it from forming a buildup and causing a clog. Repeat this monthly for the best results.
If you feel comfortable removing the cover to your condenser unit, you could also clean the fins of your air conditioner. By taking a hose with moderate water pressure, and spraying the unit from the inside out, you can effectively remove grime and buildup from the fins of your unit.
After a season of lying dormant, it's expected—even common—to notices some strange smells emanating from your air conditioner. The most common smell is dust. That's completely normal. After sitting for months, dust will accumulate in your system and the AC just needs to burn everything off.
This odor is likely a sign that there is mold or mildew in your AC's vents, ducts, or other parts. Mold inside your air conditioner may have already been there for quite some time before you see or smell it, which means that you should consult a professional as soon as you notice it.
Rotten Food
If your AC unit smells like something crawled in there and died, then that may be exactly what happened. Rats and mice often end up trapped inside air conditioners, and rodents don't smell pleasant when they pass away.
Dust, hair, and moisture on the AC filter encourage mildew growth, which can cause a musty odor when the air conditioner runs. This is a likely reason why the air conditioner smells when first turned on if you don't use forced-air heating in winter. To help prevent this odor, clean or replace the filter in the spring.
If your air conditioner smells like urine or pee, you could be dealing with a few different problems. The main ones culprits are mold again, or a coolant leak. Some people describe the scent as more like ammonia.
Rotten Eggs
The rotten egg or sulfur smell is usually a sign of a natural gas leak. Toxic air conditioner smells, like sulfur, should be taken seriously. If you smell gas, immediately turn off the gas supply and evacuate your home. Call the fire department to do an inspection.
You can get rid of the urine smell in your air conditioner by scheduling an AC maintenance and cleaning appointment. Finally, consider installing an air purifier to keep bacteria, mold, mildew, and other microbes from growing in your HVAC system.
You can prevent a clogged AC drain by performing routine cleaning. By pouring a ¼ cup of vinegar into your AC's drain line, you will kill any mold, algae, mildew, and other forms of bacteria or fungi, preventing it from forming a buildup and causing a clog. Repeat this monthly for the best results.
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The evaporator coils are found near where the cold air comes out. Wipe them down with a mixture of water and vinegar to kill microbes. At a minimum, you should clean your A/C unit at the beginning and end of each season. Optimally you should make time before it starts to cool your home.