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5 Telltale Signs of an Air Conditioner Not Working Properly billyGO Plumbing and Air Conditioning Dallas Fort Worth

If you have an air conditioner not working properly when the summer heat hits, you might think you wouldn’t miss the signs. If you’re sweating while sitting on your couch and doing next to nothing, then yes, that’s an obvious sign.

But other signs are less apparent, and they can be important indicators that you need air conditioning repair or maintenance.

It’s important to remember that your air conditioner not cooling properly can be more than an annoyance. A hot and humid house can contribute to mold growth and bug infestations, creating a health risk for everyone living there.

But if you look for the signs of an air conditioner not working correctly, including airflow, strange noises, odors, and leaks, you’ll be able to maximize air conditioner efficiency and know when to schedule an HVAC technician for A/C service.

1.   Weak or Warm Air Flow from the Vent

Central air conditioning works by taking warm air, transferring it to outside your home, and then blowing cooled air throughout a space. That’s an extreme simplification of a complex process, but it can help us understand why weak airflow from a cooling vent can be a sign of several problems with an AC unit.

Before checking the airflow from your vent, let’s make sure you understand that an HVAC system has supply vents and return vents.

  • 5 Telltale Signs of an Air Conditioner Not Working Properly billyGO Plumbing and Air Conditioning Dallas Fort WorthReturn vents pull in air from your home to deliver to your heating and cooling They are typically larger in size than supply vents. If your system is running and you hold a piece of paper up to a return vent, the paper will be pulled toward the vent.
  • Supply vents blow out the conditioned air into your indoor spaces. They are typically smaller and more numerous than the return vents in your home. It’s common to have a supply vent in nearly every room, but return vents are generally not in every room. When the HVAC system is running, a piece of paper will be blown away from the supply vent.

To check the airflow from your vent, stand on a chair or ladder and feel the air coming out. If it is blowing warm air, it could be a problem with the AC compressor or a sign that your air conditioner is low on refrigerant. If the air is cooler but the airflow is weak, it could be caused by a dirty air filter in the return vent or in the air handler, a frozen evaporator coil, air duct problems, or an issue with your blower fan.

Cleaning or replacing a dirty air filter might help the situation, and that’s something many homeowners can do themselves. But if you continue to have problems with a weak airflow from the supply vent, have a certified AC technician look at your air conditioning equipment.

2.   The Air Conditioner is Making Strange Noises

Some air conditioners are quieter than others, and older HVAC systems can be considerably louder than newer ones. But if you begin hearing new, strange noises — and it’s not some edgy new music from your teenager’s bedroom — then it could be a warning sign that your air conditioner is not working properly.

5 Telltale Signs of an Air Conditioner Not Working Properly billyGO Plumbing and Air Conditioning Dallas Fort WorthA squealing sound could mean that a component in your AC unit, perhaps a blower fan or compressor fan, needs to be lubricated, and a whistling sound might indicate a refrigerant leak. A grinding sound can be a sign of a potentially serious AC compressor problem that could lead to a pricey breakdown if the unit isn’t serviced immediately.

Other sounds that can tip you off to a problem are repeated clicking noises (usually an electrical problem), “thwapping” sounds (likely something in the blower fan) or loud clanking and banging blower assembly is the likely culprit).

Air conditioners are complex machines with a lot of moving parts, so they all will make at least some noise. But if the sounds are strange, you’re smart to be proactive and schedule air conditioning service.

3.   There is Moisture or Leakage

If you see leaks around your air conditioning system, then you’ve got a problem to address.

In some cases, it’s not serious. If water is pooling or dripping near your AC unit, it may not be a matter of the air conditioner not working, but that could be that the drain tube for condensation is blocked. An AC tech can unclog the tube and treat it with a chemical to prevent rust or mold growth that can block the tube and cause flooding.

In other cases, the moisture could be from a leak that is a serious problem. If you suspect that the leak is refrigerant, you’ll want to schedule air conditioner repair immediately. Refrigerant leaks are harmful to the environment and can also affect your family’s health.

4.   There Are Strange Odors When the Air Conditioner is Running

Any kind of strange smell is not welcome in your home, and if your AC system is to blame, it’s a stinky call to action. Some potential causes for the smell:

  • 5 Telltale Signs of an Air Conditioner Not Working Properly billyGO Plumbing and Air Conditioning Dallas Fort WorthA pungent smell could be a sign that wire insulation in your HVAC system is damaged.
  • A smell of exhaust, such as with a gas engine, can indicate a fluid leak.
  • A smell of dirty feet — yes, really, it’s sometimes called “Dirty Sock Syndrome” – often means that mildew or fungus are growing near your air conditioning equipment. It could stem from a clog that is preventing the moisture pulled from the air to properly drain, or it could be mildew in the duct and vent

If there’s a strange smell when your HVAC system is running, don’t ignore it. It might not be a serious problem, but it’s time for professional air conditioning service.

5.   My Electricity Bills are Suddenly Much Higher

Heating and cooling a home can account for nearly half of a home’s electricity use, and when the scorching heat of summer is upon us, the demands are heavy on your central air conditioning. That means electricity bills will rise during those times of peak usage. But an alarming electricity bill also might be a wake-up call for an air conditioner not working efficiently.

Some possibilities:

  • 5 Telltale Signs of an Air Conditioner Not Working Properly billyGO Plumbing and Air Conditioning Dallas Fort WorthDirty air filter: If the dirty filter restricts airflow into the ductwork, your air conditioner will need to run longer to cool your home.
  • Leaks in ductwork: The ductwork distributes air throughout your home, so if there is a leak, your AC unit will need to work harder to cool the space.
  • Mechanical failure (or reduced effectiveness): If a part of your AC unit needs repair, the entire system becomes less efficient and requires longer run times.
  • Low refrigerant: If your AC unit doesn’t have enough refrigerant, then it will need to run longer to keep your home cool. Low refrigerant levels are usually caused by a leak, and you’ll need an air conditioning pro to diagnose the problem.

OR — Could the Thermostat Be Failing?

A thermostat not working properly isn’t as much a sign that your air conditioner is not working properly as a reason your air conditioner isn’t working properly. If a thermostat fails, the air conditioner might not turn on at all because the room temperature cannot be read correctly.

5 Telltale Signs of an Air Conditioner Not Working Properly billyGO Plumbing and Air Conditioning Dallas Fort WorthTo make sure your thermostat is working right, check that the thermostat is turned to the “on” position and is set for cooling, not heating. (Yes, this seems obvious, but sometimes a setting gets changed accidentally).

Lower the temperature setting a few degrees below the thermostat’s reading of the room temperature. If the air conditioner doesn’t start running within a few minutes, an HVAC technician should check your thermostat and other air conditioning equipment.

If you do need to replace it, having an air conditioning pro install a programmable thermostat can help your system run more efficiently and save you money.


Central air conditioning is a modern marvel, but it’s also a complex system that requires maintenance. So, as you try to stay cool during the hottest months of the year, look for the signs of your air conditioner not working properly:

  • Weak or warm airflow
  • Strange noises, such as banging, clanging, squealing or whistling
  • Unpleasant Odors
  • Moisture or puddles of water around the AC equipment
  • Surprisingly high electricity bills

Some of the problems, such as a faulty thermostat, might not be serious, while others could be warnings that a major air conditioning breakdown is on the horizon. Either way, scheduling an air conditioning tune-up can address potential problems and help you avoid more costly repairs.

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