Why Is My AC Not Dehumidifying?

August 17, 2022

Is your Tampa home getting too humid?

Your air conditioner keeps you cool and comfortable in the summer by doing two main things: reducing the air temperature and removing moisture from the air. If you feel uncomfortably sticky and sweaty in your home, your AC probably isn’t dehumidifying properly.

The most common AC problems that can cause high humidity levels in your home are:

  • A refrigerant leak
  • A dirty air filter
  • Dirty evaporator coils
  • An incorrect thermostat fan setting
  • An oversized AC

We’ll explain each of these issues and offer solutions. But first, let’s take a quick look at how your AC is supposed to dehumidify your home under normal conditions.


Need a pro to inspect your AC?

Call Red Cap. We offer same-day AC inspections and repairs, and we’ll even waive the diagnostic fee if you hire us to complete the repair. Call (813) 963-3056 (Tampa) or (727) 474-8287 (Pinellas) or schedule your AC service online.


How Your AC Dehumidifies Your Home

Your AC has an evaporator coil that sits in your indoor unit. It’s an A-shaped web of copper coils that absorbs the heat and moisture from the air with refrigerant (a heat transfer fluid).

As the moisture accumulates on the evaporator coil, it drips into a condensate pan and drains away through the condensate line that leads outdoors. Your home’s humidity levels drop as the moisture drains outside.

Unfortunately, certain AC problems can sometimes hinder this dehumidification process, making your house feel sticky and uncomfortable. Let’s look at those possible issues.

A Refrigerant Leak

Is your AC leaking refrigerant?

Since refrigerant attracts heat and moisture from the air inside your home, low refrigerant levels will reduce your AC’s ability to dehumidify properly.

Closed copper coils hold the refrigerant that runs through the AC unit, so it shouldn’t escape the system. The only reason your AC would be low on refrigerant is if you have a leak.

Common signs of a refrigerant leak are:

  • High humidity levels in your home
  • Warm air coming from your AC vents
  • An AC bill that’s higher than normal
  • Hissing or bubbling noises coming from your AC unit
  • Ice on the refrigerant lines or evaporator coil
  • An AC that struggles to cool your home

How to fix it: If you think you have a refrigerant leak, you’ll need to hire a professional to inspect your AC, fix the leak, and then recharge your system.

A Dirty Air Filter

A dirty AC filter prevents your system from dehumidifying the air properly.

A dirty air filter restricts the AC’s airflow, which means it won’t be able to cool and dehumidify as much air.

If a thick layer of dirt and dust is covering your air filter, your AC will also have to work harder and longer to cool your home efficiently. So you can expect to see higher electricity bills as your system struggles to cool your home. How to fix it: Replace your dirty, clogged AC filter with a clean one and continue to do so every month or two. This will help lower the humidity levels in your house and reduce your air conditioner's energy consumption by 5% to 15%, according to Energy Saver. That means your electricity bill should go back down too.

Dirty Evaporator Coils

Dirty AC evaporator coils can cause system breakdowns.

Over time, your AC’s evaporator coils can get caked with dirt. A thick layer of dirt and dust on the coils will act as insulation, preventing them from absorbing heat and moisture from the air.

With dirty evaporator coils, your AC will run longer no matter what, and it will struggle to do its job of cooling and dehumidifying your home. It’s also more likely to break down frequently due to the increased wear and tear on the system.

How to fix it: Hire a professional to inspect and clean your AC’s evaporator coils. They will be able to clean them properly and carefully to avoid damaging the part.

An Incorrect Thermostat Fan Setting

Check that your thermostat is on the right settings.

If you set your thermostat to ON instead of AUTO, your AC will struggle to dehumidify your home. That’s because the ON setting ensures that the system’s fan blows continuously, wicking the moisture on the evaporator coils back into your home instead of giving it time to collect on the coils and drain away.

On the other hand, setting your thermostat to AUTO ensures the fan will only run during cooling cycles. So when it shuts off, the moisture absorbed by the cooling coils will collect and drain outdoors through the condensate drain line.

How to fix it: Check your thermostat. If you have it set to ON, change it to AUTO.

An Oversized AC

If your AC is too big for your home, it will run in frequent and short bursts (called short-cycling), preventing it from dehumidifying your home.

Here’s why:

Moisture collects on the evaporator coils as your AC runs and then exits your home via the condensate drain line. This process works best when the AC runs in long and steady cycles. If your AC doesn’t run long enough, there won’t be enough time for the moisture to collect on the coils, drip off, and then drain away. Instead, all that moisture will stay inside your home.

An oversized AC will reach the desired temperature inside your home very quickly and shut off before the moisture has had time to accumulate and exit your home. It will continue to run in short bursts like that, cooling your home but never dehumidifying it, leaving you feeling sticky and sweaty.

How to fix it: A professional can inspect your AC system and determine whether it’s too large for your home. If so, they may recommend replacing it with a smaller system. Doing so will eliminate your high humidity issues, reduce your energy bills, and increase your system’s lifespan.


Need AC Service From a Tampa or Pinellas Tech? Call Red Cap!

Contact Red Cap for consistently high-quality AC service.

If your AC isn’t dehumidifying your home, we can quickly help you solve the problem. Whether you need an AC repair or AC installation, you can count on us to get the job done right and honor our service guarantees. Our Red Cap family has built a reputation for consistent, quality service. Just check our 5-star reviews to see why Tampa families continue to rely on us for all their HVAC needs. Just call (813) 963-3056 (Tampa) or (727) 474-8287 (Pinellas) or schedule your AC service online.


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