Are you getting musty, dirty sock type air conditioner smells from your HVAC unit? If so, then you’ve come to the right place to find a solution, and get your home smelling so fresh and so clean.
The very first thing that you should check would be the air filter. That’s usually the cause of it. If the air filter is clogged and dirty, that may also mean that the evaporator coil is plugged, with dirt, dust, and possibly bacterial growth.
There will be standing condensation feeding these bacteria that will not allow the condensation to fall off the evaporator coil into the drain pan. This is what mainly causes musty air conditioner smells in your home whenever the HVAC unit cycles on. Some in the HVAC industry have called this dirty sock syndrome.
If the evaporator coil is plugged, there’s going to be standing condensate on all that crud, creating a musty smell from the air passing through it. To remedy this, you need to chemically clean the evaporator coil.
How to Clean an Evaporator Coil
- Turn off the air conditioning unit and remove the filter
- Put on your safety glasses and chemical proof gloves
- Get a bristled brush, toilet brushed work great for this.
- Brush the evaporator coils, going in the same direction as the coil. This is usually up and down. Don’t brush side to side as you don’t want to bend the coil fins.
- Spray the evaporator coil with coil cleaner. You should probably use a pressurized pump sprayer for this.
- Brush the coils again.
- Rinse the coils with hot water.
- Repeat until clean and shiny. Clean up the mess you made.
Next step to getting rid of a smelly air conditioner is to check the drain pan, and clean if necessary. If your coils were dirty, then more than likely your drain pan is as well.
How to Clean a Drain Pan in a Furnace
- Turn off the power to the unit.
- Using the coil cleaner, spray and brush the drip pan. Use a soft, small toilet brush.
- With a wet/dry shop vacuum, vacuum up the water.
- Flush the pan with hot water, this will also ensure that your A/C drain line isn’t clogged
- Wipe down the insulation, and everything inside of the air handler/furnace
There are specific tabs that are made for air conditioner drain pans. They are supposed to prevent, or slow down bacterial growth. I’ve yet to find a product that actually does this, but some of the tabs do have a nice scent to them.
Completing these two checks in most cases will get rid of those musty air conditioner smells, or dirty sock syndrome.
Still Getting Wet, Musty Air Conditioner Smells Coming from Your Unit?
It may be time to buckle down and call for professional service. If you are a beginner HVAC technician, and don’t know where to look next, then read on young apprentice.
Check the blower motor wheel for signs of bacteria and build up. If your blower motor wheel is caked with dust, this can also cause unpleasant odors in your HVAC system. Blower motor wheels that are extremely caked with debris may also start to wobble and spin off balance, decreasing your air efficiency.
How to Clean a Dirty Indoor Blower Assembly (Recommend Pros Only)
- Disconnect power to the furnace, and unhook the quick connect to the blower motor electrical
- Remove the screws that are securing the blower motor assembly.
- Pull out the blower motor assembly and take it outside
- Remove the motor from the blower motor casing
- Take the wheel off the blower motor shaft by loosening the set screw. Some older motors may be locked on to the shaft. Some cases it will require lubrication and a motor pulley to get the wheel disconnected from the blower motor shaft.
- With the blower motor wheel off the motor, spray with coil cleaner, and wash with a garden hose.
- Once it’s nice and shiny, reinstall the blower motor assembly.
Most of the time completing these steps will get rid of most nasty air conditioner smells, or dirty sock syndrome. If you are still getting complaints of your air conditioner smelling, it may be time to get your air ducts inspected, and possibly cleaned.
Preventing your Coil from Growing Bacterial Growth
If your air conditioner smell goes away after chemically cleaning the evaporator coil and drain pan, there’s a chance that the dirty sock syndrome may come back. There are a couple of options to prevent, or slow this down.
Upgrade your air filter to the highest MERV rating your system can handle.
Some experts say that Ultra Violet lamps installed before the coil and after the coil can also kill any kind of bacteria growth on the evaporator coil. Although this helps, it’s still not a 100% solution.
If you’ve tried all the above, and that musty air conditioner smell keeps coming back, then you may need to replace the evaporator coil, and have the evaporator coil coated to prevent bacterial growth on it. This is the most expensive option. If your air conditioner system is more than 10 years old you may want to look into replacing your unit.
Burning Smell from Air Conditioner
There are a few types of burning smells that can come from your air conditioner furnace. The most common is when you first turn on your heater for the first time of the season. Dust will build up on your blower assembly, gas furnace tubes, electric heater, whatever you have. When that heat kicks on, you are smelling that burning. This will usually go away after a couple of minutes.
The other type of burning smell is may be wires burning. This will jump out at you as the smell of wire insulation, or duct insulation, will be strong. This will usually also be follow by smoke, and possibly failure of your furnace. If this is the case then call for service. If there’s smoke coming out of the vents, you may want to call 911.
Final Thoughts on Funky Air Conditioner Smells
If you are a technician and get the complaint of an air conditioner smelling musty, then you know there’s a good chance you’re dealing with dirty sock syndrome.
There could also be different scenarios of why your air conditioner smells though that may not have been covered in this article. I’ve found dead rats before behind an air return grill before, which doesn’t smell musty or like anything’s burning. It just smells BAD.
Have any stories or concerns to share about bad air conditioner smells? Drop a comment, or a picture below and let’s get this conversation going!