7 Reasons Your AC is Not Cooling Properly (Easy Fixes)

Summertime is the best time of year, right?

Well, usually, with the mercury rising into triple digits day after day, it can be tough to keep cool without air conditioning. But if your AC unit is on the fritz, summer can quickly become a living nightmare.

There is no reason why air conditioning units should not cool and last for as long as 10-15 years. However, if you feel that your air conditioner is not cooling or performing to its potential, it could be due to several common reasons, such as the air filter becoming dirty and choked, and plants, leaves, and other debris obstructing the external unit.

So, before you reach for your phone to call an HVAC technician, try troubleshooting some common air conditioning issues yourself.

In this blog post, we’ll outline some of the reasons why your air conditioner is not cooling as it should and how to fix them. We will also offer some tips on how to maintain your unit so it runs smoothly all season long.

Air Conditioner Not Cooling – Common Causes and Fixes

Summer’s here—and instead of relaxing in cool comfort, you’re stuck sweating like you’re in a sauna. Before you blame the cosmos or Mercury retrograde, it’s time to take a closer look at your air conditioner. Often, the issue isn’t major—just overlooked.

Below are 7 common (but fixable) reasons your AC might not be cooling effectively—and what to do about each one. Some are easy DIYs, while others need a professional’s expertise. Either way, solving them now can spare you serious discomfort (and expense) later.

1. Clogged Air Filters

Imagine trying to breathe through a thick layer of dust—that’s exactly what your AC goes through with a dirty filter. Blocked airflow forces your system to work harder, reduces cooling efficiency, and can even cause long-term damage.

Pro Tip: Check your filter every 1–3 months (or monthly if you have pets or allergies). If it looks dark, dusty, or clogged, replace it immediately. Clean filters mean better airflow, better performance, and lower energy bills.

You can buy the new Filtrete AC Furnace Air Filter from major retailers like Amazon, Home Depot, Lowe’s, or directly from the Filtrete website. These are available in a variety of sizes and MERV ratings to suit different HVAC systems and filtration needs, whether you’re looking to trap basic dust or capture allergens like pollen, pet dander, and smoke.

They’re also easy to install, and replacing them every 60 to 90 days can help your AC run more efficiently and keep your indoor air fresher.

2. Thermostat Set Incorrectly

Sometimes, the solution is surprisingly simple. If your thermostat is set to the wrong mode or temperature, or the batteries are dead, your AC might not even know it’s supposed to be cooling.

Pro Tip: Ensure the thermostat is set to cool, not heat or fan. Set the temperature lower than the room temperature, and replace the batteries if it’s been a while. A working thermostat = a working AC.

3. Refrigerant Leaks

If your AC is running but the air isn’t cold, you may have a refrigerant leak. Refrigerant is essential to absorb and release heat. When levels are low, your system struggles—and your comfort suffers.

Pro Tip: Signs include hissing noises, ice on coils, or weak cooling. This isn’t a DIY job—call a licensed HVAC technician to inspect, repair, and recharge the system.

4. Faulty Compressor or Capacitor

The compressor is the engine of your AC; the capacitor helps it start. When either fails, your system can’t cool. You might hear humming, buzzing, or nothing at all—while the fan may still run, giving a false sense that all is well.

Pro Tip: If your system won’t start or shows erratic behavior, shut it off immediately and call a technician. Electrical components can be dangerous—don’t take the risk.

5. Blocked Outdoor Unit

The outdoor condenser unit releases heat from your home. But if it’s covered in weeds, leaves, or debris, it can’t function properly.

Pro Tip: Maintain a clear 2–3 foot radius around the unit. Turn off power and gently clean the coils with a garden hose (never a pressure washer). A little outdoor care can go a long way in improving performance.

6. Leaky Air Ducts

Leaky ducts are like trying to sip through a cracked straw—cool air escapes before it ever reaches your rooms. If some areas stay warm or your utility bills are unusually high, leaks might be the cause.

Pro Tip: Hire a professional to test and seal duct leaks properly. If you’re sealing small leaks yourself, use mastic sealant or foil-backed tape (not standard duct tape—it doesn’t hold up).

7. Undersized AC Unit

If your AC never stops running and still can’t keep your space cool, it might be too small for your home’s size—especially after a renovation or room addition.

Pro Tip: A qualified HVAC professional can do a load calculation to determine whether your system is properly sized. If not, you may need a larger unit or a supplemental cooling solution.

Why are Strange Noises and Smell Emanating from MY AC Unit?

If your air conditioner has recently started sounding like a haunted dishwasher or smelling like a damp gym sock—don’t panic (yet). You’re not losing it, and your AC isn’t possessed. But it is trying to get your attention.

Strange noises and funky smells coming from your air conditioner are warning signs that something’s not quite right.

And ignoring them? That’s like turning up the radio to drown out engine noise—it doesn’t solve the problem, it just delays the inevitable (and often more expensive) fix.

Weird Noises: Your AC’s Cry for Help

Rattling, buzzing, clanking, or squealing? That’s your AC’s way of saying, “Hey! Something’s loose, broken, or stuck in here!”

• Loose parts: Screws, bolts, or panels may have wiggled free over time—kind of like your patience on a hot day.
• Debris or obstructions: Leaves, twigs, or worse (hello, curious critters) might be lodged inside the unit.
• Worn-out motor or bearings: If the noise sounds more mechanical—like grinding or humming—it’s likely internal wear and tear needing attention before it escalates into a costly repair.

If your AC’s making sounds it shouldn’t, it’s not just “being old.” It’s being ignored. Get it inspected before minor issues become major breakdowns.

Unpleasant Smells: More Than Just a Bad Vibe

Now, about that funky smell—musty, sour, or just plain gross? It’s probably not your teenager’s socks hiding in the vents. It’s bacteria.

Warm, damp areas inside your AC, like the coils or drain pan, are a playground for bacterial and mold growth. And as this gunk builds up, it releases methane and other nasty gases into your airflow. That’s what you’re breathing in. Gross, right?

But here’s where it gets worse:
These microbes don’t just stink. They can aggravate allergies, trigger asthma, and even affect your immune system over time, especially for kids and the elderly.

What You Should Do Before It Gets Worse?

If your AC is noisy, smelly, or both, it’s not just an annoyance—it’s a problem waiting to grow mold, damage parts, or shut your cooling down altogether.

Don’t mask it with air fresheners or noise-canceling headphones. Call a licensed HVAC technician to give your unit a thorough inspection and cleaning. That means clearing out the bacteria, tightening the loose parts, and restoring your AC to clean, cool, quiet bliss.

Why is Water Leaking from the AC and What You Should Do About It?

If your AC is leaking water, it’s not trying to ruin your day—it’s trying to tell you something’s wrong.

A little condensation? Totally normal. But steady drips or unexpected puddles? That’s your cue to stop scrolling and start investigating.

Water leaks can lead to mold, water damage, and, if ignored long enough, a meltdown worthy of a drama series.

Here’s the cast of usual suspects:

1. Clogged Condensate Drain Line

Your AC isn’t just blowing cool air—it’s also quietly battling humidity. All that moisture needs somewhere to go, and that’s where the condensate drain line comes in.

But when that line gets clogged with dust, grime, or the ghost of maintenance past, the water backs up and spills out like a teenager’s soda on movie night. Not ideal.

2. Faulty Float Switch

The float switch is like your AC’s guardian angel—it senses when water levels get too high and shuts the system off before things get messy.

But if it’s stuck or acting up (float switch mood swings?), your unit keeps running while water piles up until—splash—there’s your leak.

3. Other Culprits Lurking in the Shadows

• Rusty or cracked drain pan: Think of it as your AC’s drip tray. If it’s old and corroded, water’s bound to escape.
• Low refrigerant levels: This can cause your coils to freeze over, and when they thaw, it’s rainstorm time.
• Poor installation or insulation: If the system wasn’t installed properly, or the insulation is lacking, you might get more condensation than you bargained for.

Here’s the deal: the longer you wait, the more expensive the fix. Water damage isn’t just annoying—it’s mold’s best friend and your home’s worst enemy.

Call in a pro ASAP. A quick check-up now could save you a major headache (and wallet ache) later.

Additional Tips for Maintaining Your Home Air Conditioner to Extend Its Life

If you regularly maintain your air conditioner, it will not only cool better but also save you a lot of money in power consumption and eliminate breakdown repairs.

1- Keep It Clean

The reason why air conditioners do not operate efficiently and ultimately break down is surprisingly something as common as the buildup of dirt and dust.

Because the air filter is tucked away out of sight, it is straightforward to forget all about it, even though you may know that it is an essential component.

However, you should make it a point to have a schedule that makes it mandatory to clean it once a month during the summer and once in three months at other times of the year when the unit is being used more sparingly.

Not only will you be breathing cleaner air, but you will also save a lot of money in reduced power consumption as the unit cools far more efficiently.

2- Bi-Annual Maintenance

Ensure that your air conditioner is inspected at least twice a year for any signs of problems that could lead to expensive repairs later on.

All the unit’s main components should be inspected, including the coils of the condenser and the evaporator.

Check if the level of refrigerant is okay, as in case it has dipped, there is likely a leak, which must be attended to immediately. This is because the fluids are highly toxic and may cause respiratory problems to those in their proximity.

The bi-annual maintenance will also reveal in case there are any electrical issues, such as overheating or losing contacts, that may lead to sparking and short circuits.

3- Attend Repairs Immediately

In case the inspection reveals an issue, or you perceive that your air conditioning unit does not seem to be working as well as expected, it becomes essential that your unit is repaired urgently before it escalates to something much more severe and expensive.

Identifying faults can be tricky for a layman, so you should call in the experts. It is vital to resist the tendency to wait till the suspected problem balloons out of control and becomes an emergency.

4- Keep the Room Tightly Closed

Making sure that the room in which the air conditioner is installed is always kept shut, even when you are not using it, will also help make it more energy-efficient.

In case it is not too hot, you could use the fan mode to circulate the air in the room. Or you can use a humidifier with an AC, which will also help reduce power consumption.

5- Use a Programmable Thermostat

This is one way in which you can save on your power bill, as you can set the temperature higher when you are not at home and lower it just before you arrive. In this way, you will be using the unit only when you need it and not all day long.

An added advantage of using a programmable thermostat is setting different temperatures for different times of the day.

6- Do Not Use it as a Dehumidifier

While air conditioners do remove some moisture from the air, they’re not designed to function as full-on dehumidifiers. Their main job is to cool your space by removing heat, not humidity. If you live in a very humid area and rely solely on your AC to dry out the air, you’ll likely end up with less comfort and higher energy bills.

If you’re battling sticky air, consider using a standalone dehumidifier along with your AC. This combo lightens your AC’s load and helps maintain a cooler, drier, more comfortable environment, especially in basements or during monsoon season.

7- Educate Everyone at Home about Conserving Energy

Last but not least, educating every household member about conserving energy is important. This is especially important if you have young children at home who may not know the importance of saving power.

By following these simple tips, you can not only prolong the life of your air conditioner but also make it more energy-efficient. Not to mention the money you will be saving in terms of reduced power consumption.

Conclusion

It is advisable to have your air conditioner serviced at least twice a year in order to keep it running smoothly and efficiently. This will also help to avoid any potential repair costs in the future.

Ideally, you should clean or replace your air conditioner filter every month. However, this may vary depending on the type of filter you have.

Careful and appropriate air conditioner maintenance will not only allow the unit to perform efficiently but also enable you to avoid premature and emergency failures that can take a lot of money to repair or replace the unit.

With preventive maintenance, you can easily extend the life of the unit considerably, as well as keep running costs down.