10 Common AC Maintenance Problems And How To Fix Them

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Hands working on AC unit

If you’re like most homeowners, you probably don’t give much thought to your air conditioning unit until it stops working properly. But if you want to avoid costly AC maintenance problems, it’s important to be aware of the most common issues that can arise.

In this blog post, we’ll take a look at 10 of the most common air conditioner problems and offer tips on how to prevent and fix them. So whether your AC is brand new or has been around for a few years, keep reading for helpful advice.

*Remember to disconnect power to your air conditioner unit before attempting any repairs!

1. Air Conditioning System Not Cooling

Ah, the cooling comfort of central air on a sweltering summer day. But when your air conditioner unit suddenly starts blowing hot air, it can feel like the worst possible news on the hottest day of the year.

Rest assured, you’re not alone—nor do you have to resort to sleeping in your fridge to make it through the next few days until a repair person can come out. In fact, this is probably the most common AC problem. Here are some of the most common causes of this AC problem, as well as the best solutions to this issue.


If your unit is not cooling properly, the first thing you should check is the thermostat to make sure it’s set correctly. If the thermostat is fine, then move on to the next possible cause: a clogged air filter.

Air Filter Clogged

If your AC unit isn’t cooling your home as effectively as it used to, another thing you should check is the air filter. If it’s clogged, replace it with a new one. A clogged filter makes it difficult for air to circulate and can put unnecessary strain on the cooling system. 

If that doesn’t fix the problem, there could be an issue with the refrigerant levels.

Low Refrigerant Levels

Another common cause for an air conditioner not blowing cool air is low refrigerant levels, also sometimes referred to by the brand name Freon. The best way to ensure that you have proper levels of refrigerant is to contact a qualified AC repair technician.

Evaporator Coils Dirty Or Frozen

Cleaning ac coil using water

Another common cause for an air conditioner unit not blowing cool air is dirty evaporator coils. Cleaning off any debris or simply replacing dirty coils can usually solve ac maintenance problems like this.

Evaporator coils can also freeze if there’s not enough airflow over the coils, which can happen for a variety of reasons—including a clogged air filter or dirty evaporator coil.

If this is the case, you’ll likely see ice or frost on the coils themselves. Fortunately, thawing out the coils is usually a pretty simple fix; just turn off your AC unit and let the coils thaw for about an hour. Once they’re thawed, check your filters again and clean or replace them if needed. 

Damaged Compressor

Another potential cause for your AC not cooling is a damaged or broken compressor. Unfortunately, if the compressor is damaged, you will likely need to replace the entire unit. 

2. Air Conditioner Is Leaking Water

Air conditioner leak causing wall stains

If you’ve ever come home to find a puddle of water around your air conditioner, you know how frustrating it can be. A little bit of condensation is normal, but if your unit is leaking large amounts of water, it could be a sign of more serious AC maintenance problems.

Not only is leaking water unsightly, but it can also lead to serious damage to your home if left unchecked. The good news is that there are a few things you can do to prevent your AC from leaking water.

Clogged Condensate Drain Line

If your air conditioner is leaking a lot of water, it could be a sign of a clogged condensate drain line. When the drain line becomes clogged, water backs up and spills out of the unit. To clean it out, turn off your unit and remove the access panel. Locate the drain line and use a stiff wire or plumbing snake to clear any blockages.

Clogged Condensation Pan

Another common cause of leaking water is a clogged or debris-filled condensation pan. To fix this AC maintenance problem, simply clean out the condensation pan or replace it entirely.

Evaporator Coil Failure

Another possible cause is the failure of the evaporator coil. If the coil is leaking, it will need to be replaced. Again, this would be the time to call in a professional AC repair person.

AC Unit Is Not Level

Make sure that your air conditioner unit is level; if it’s tilted, water could be coming out through the sides instead of going into the condensation pan.

AC Unit Has Cracks Or Holes

You should also check the outdoor unit for any cracks or holes that could be letting water in. If there are any, you may need to contact an air conditioner professional to fix them. If it’s bad enough, you may need to buy a new unit.

3. AC Making Strange Noises

Woman with ac maintenance problems

One of the most annoying AC maintenance problems that can happen is when it starts making strange noises. Not only is it distracting, but it can also be a sign that something is wrong with your air conditioner unit.

Unusual noises coming from your air conditioner unit can be caused by anything from loose screws to a failing compressor. If you hear rattling, popping, or grinding sounds, turn off your air conditioner unit and run through the following list of possible causes.

Dirty Air Filter

First, check the air filter. A clogged air filter can restrict airflow and cause all sorts of problems, including strange noises. If it’s dirty, clean or replace it.

Loose Fan Blade

If your unit starts making strange noises, it could be due to a loose fan blade. Tightening the screws holding the fan blade should fix this problem.

Damaged Motor Mount

A damaged motor mount can cause a rattling noise when the AC unit is running. Replacing the mount should take care of this AC maintenance problem. This may not be the most do-it-yourself-friendly problem to solve.

Frozen Evaporator Coils

Evaporator coils can become frozen, which will cause them to make strange noises. To thaw the coils, simply turn off the AC and let it thaw for a few hours. Once the coils are thawed, you should be able to use your AC without any problem.

Broken Compressor

If your air conditioner is making strange noises, it could be a sign that the compressor is damaged. The compressor is responsible for circulating refrigerant through the AC system, and if it isn’t working properly, the entire system can suffer. 

If you suspect that your AC compressor is damaged, it’s important to have it checked by a qualified technician. They will be able to diagnose the problem and recommend the best course of action. In many cases, a replacement compressor will be required. 

4. AC Isn’t Turning On

Hand over air conditioning because it won't turn on

Let’s face it; there are few AC maintenance problems more frustrating than your air conditioner not turning on when you need it most. Fortunately, there are a few things you can check yourself before it’s time to call in a professional air conditioning technician.


Make sure that your thermostat is set to “cool” and that the temperature is lower than the current indoor temperature. If that doesn’t solve the issue, it’s time to check your power supply.

Power Supply

Make sure that the unit is properly plugged in and receiving power and that the circuit breaker hasn’t been tripped. 

Compressor, Capacitor, Or Coils

If the problem persists, there may be an issue with the compressor, the capacitor, the coils, or another major component of the unit. The best way to fix this is to call a professional for AC maintenance. They can take a look at your unit and make any necessary repairs or part replacements.

5. Thermostat Isn’t Working



Check to make sure that the batteries in your programmable thermostat are still good. If your programmable thermostat uses AA or AAA batteries, simply replacing them may do the trick. 

Reset Thermostat

Try resetting the thermostat by turning it off and then back on again after 30 seconds have passed.


If replacing the batteries or resetting the thermostat doesn’t work, there could be an issue with the wiring. After making sure the power supply is disconnected from the AC unit, check for any loose or damaged wires. Tighten or replace them as necessary. 

If you’re still experiencing AC problems, you’ll need to contact a qualified HVAC technician to diagnose the issue and recommend a solution.

6. Frozen AC Coils

Ah, the frozen AC coil. One of the most frustrating issues to experience, especially during those dog days of summer. The air conditioning unit is working overtime, and, as a result, the coils freeze. Why does this happen? Let’s take a look at the most common causes of this problem.

Dirty Air Filter

Once again, make sure that you’re regularly changing your air filter. This should be part of the routine maintenance checklist. A dirty filter can cause your air conditioner unit to work harder than necessary, which can lead to ice buildup on the coils. 

Low Refrigerant Levels

When the level of refrigerant in your unit gets too low, it can cause the coils to freeze. This can happen for a variety of reasons, but the most common is a leak in the system. To thaw them out, turn off your air conditioner unit and let it sit for a few hours.

Whatever the reason, it’s important to have a professional check your system and properly recharge it. Otherwise, you could end up damaging your air conditioner unit and shortening its lifespan. 

7. Dirty Air Filters

New and clean ac filter vs old and dirty ac filter

As previously noted, dirty air filters can cause multiple problems with your AC unit. Replacing dirty air filters is one of the most effective ways to maintain your AC unit and prevent common problems from arising. Fortunately, this is also one of the easiest problems to fix!

Simply locate the filter (it will either be in the return air duct or inside the blower unit) and remove it. Vacuum any dirt or dust off of it, then rinse it with water. Let it dry completely before putting it back in place. 

For optimal results, replace disposable filters every 1 to 3 months. 

8. Clogged Condenser Unit

Person cleaning dirty condenser coils on an air conditioner system

The condenser unit is responsible for dissipating heat from the refrigerant. It does this by circulating air over the coils. Any homeowner with one of the types of central air conditioning knows that a clogged condenser unit can be a real problem.

Not only does it cause the unit to work less efficiently, but it can also lead to costly repairs. This is why routine air conditioner maintenance is so important.

So what AC maintenance problems can cause a clogged condenser unit?

Dirty Coils

If the coils are dirty, the condenser unit will not be able to dissipate heat effectively. As a result, the refrigerant will become overloaded and will start to back up into the evaporator coils. This can cause many AC problems, including reduced cooling capacity, reduced efficiency, and even complete failure of the AC unit. 

To clean the coils, simply turn off power to the unit, remove the condenser unit, and clean the coils with a brush attachment on a vacuum cleaner. Be sure to use gloves and eyewear to protect yourself from any sharp edges.

Fan Not Working

If the fan is not working correctly, the condenser unit will not be able to remove the warm air caused by the operation of the air conditioner unit. This can sometimes be caused by debris buildup or even an animal nest inside the unit.

To fix this, try removing any debris that may be preventing the efficient operation of the fan. The best way to clean it is with compressed air. Just aim the nozzle at the fins and blast away!

You can also use a brush attachment on your vacuum cleaner, but be careful not to bend any of the fins. If that doesn’t resolve the issue, you’ll need to contact an air conditioner maintenance technician to help you diagnose the problem.

9. Leaky Ducts Or Vents

Leaky ducts or vents can decrease the efficiency of your air conditioner unit and send conditioned air into the attic or other unwanted places in your home. This problem can decrease airflow and waste energy, so it’s important to seal them up as soon as possible.

The best way to do this is with mastic sealant or metal tape. Just apply either one over any holes or gaps in the ductwork. You can also use caulk around vents where they meet walls or ceilings.  

10. Faulty Compressor

Working on outdoor compressor unit air conditioner

The compressor is the heart of your AC system, pumping refrigerant through the coils. The trouble with this part can be serious. Here are some of the most common AC maintenance problems that lead to a faulty compressor.

Dirty Air Filter

By this point, you are probably realizing the importance of keeping your air filter clean! A dirty filter can cause all sorts of AC problems, including a faulty compressor. 

Low Refrigerant Levels

Take a look at your air conditioner’s refrigerant levels. If they’re low, that could also be causing your compressor to malfunction. An air conditioner maintenance technician can refill it for you.

Loose Wiring

Check for any loose wires or other damage to your air conditioner unit. Before attempting to tighten any loose wiring, ensure that the power is disconnected from your unit! Anything involving electricity is dangerous. It’s best to have an air conditioner maintenance professional handle it.

Contact Confident Comfort Heating And Cooling

No matter what type of problem you are having with your air conditioner, it’s always best to call an HVAC professional for help.

If you’re experiencing AC maintenance problems, fill out our contact form today–we will be able to diagnose the problem quickly and get your AC unit up and running again in no time!