The bottom line: Your AC has 2 jobs—to cool your home and dehumidify it.
So if you’ve noticed that your AC isn’t dehumidifying your home, you most likely have one of the following problems:
We’ll explain each of these problems and how you solve them. First, though, let’s look at how your AC is supposed to dehumidify your home during normal operation.
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During normal operation, your AC pulls in warm, humid air from inside your home. That warm air passes over very cold evaporator coils. Those coils are designed to pull both heat and moisture out of the air.
An AC evaporator coil pulling heat out of the air.
After this process, all that’s left is cold, dehumidified air that gets pushed back into your home.
So what happens to all the moisture that’s absorbed from the air?
The moisture from the air slowly collects on the evaporator coils then drips down into a drain pan. As the water level in that drain pan rises, the moisture drains away outside via the condensate drain line (see below).
The dehumidification process of an air conditioner.
So if your AC isn’t dehumidifying your home, there’s something wrong with this process.
Learn more about the AC process in our blog, “What Does an Air Conditioner Actually Do (And Why it Matters)”.
Let’s look at some of the reasons your AC might not be dehumidifying your home…
Before calling a pro, check your thermostat.
If you notice that the fan is set to ON, this is likely what’s preventing your AC from dehumidifying your home.
Why? Well, your AC fan is designed to run only during cooling cycles then shut off. When the fan shuts off, all the moisture absorbed by the cooling coils has time to collect and drain away outside (via the condensate drain line).
If the fan is blowing non stop, though, all that moisture sitting on the coils is blown right back into your home.
The solution: Make sure your thermostat fan is set to AUTO, never ON.
Your evaporator coils are responsible for absorbing the heat and moisture from the air inside your home. But if they’re covered in a layer of dirt, they can’t do their job very well.
The result? Your AC will run longer and struggle to cool or dehumidify your home.
The solution: Have a professional inspect your evaporator coils and clean them if needed.
Your air conditioner uses refrigerant to move heat and moisture out of your home and dump it into the outside air.
Over time, though, the lines that hold the refrigerant can develop leaks from normal wear and tear. If this happens, your AC has less cooling and dehumidification power.
Signs that your AC has a refrigerant leak include:
The solution: Have a professional inspect your AC lines for a leak, fix it and then recharge your system.
Almost all ductwork is leaky to some extent. In fact, Energy.gov estimates that the typical home loses upwards of 30% of conditioned air to leaks in ductwork.
The bad news is that if your ducts are located in the attic, basement or crawl spaces, these leaks could be pulling humid, dirty air into your home.
Signs you have leaky ductwork include:
The solution: Have a professional inspect your ductwork to see if duct sealing would work for you.
If your air conditioner is too big for your home, you’ve likely always noticed high indoor humidity levels. You see, when an air conditioner is oversized for your home it cools your home quickly, shuts off then turns back on after a short period.
This “on-then-off-again” process is called short-cycling. Short-cycling prevents the AC from ever dehumidifying your home. That’s because the dehumidification process works best when the air conditioner has longer, steadier cooling cycles.
The solution: Have a professional inspect your home and AC system to determine if the unit is too big for your home. If it is, you may want to consider replacing it with a smaller unit.