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Updated July 28, 2020

It’s a dreaded experience for many homeowners: their normally cool house starts to feel hot as the air conditioner makes strange noises and starts to falter. Is it time to call an HVAC technician? Troubleshooting air conditioning can potentially save you thousands of dollars and lots of time and stress.

Below is a complete guide to common AC issues to help with troubleshooting residential air conditioner problems:

Why Is My Air Conditioner Making Strange Sounds?

Your air conditioner is probably one of the most used and important parts of your home. It’s responsible for keeping your house cool and comfortable. When an air conditioner is working properly, it often goes unnoticed. But once it starts making strange noises, you likely start to notice it and wonder what needs to be fixed. When it comes to heating and cooling, it helps to know what causes strange sounds. Here are seven noises AC units might make and what they could mean.

Squealing Sound

A high-pitched squealing sound from your air conditioner can be unsettling. In many cases, the sound comes when the belt that connects to the motor slips. If this is the case, you’ll hear the sound both inside and outside your home and the belt needs to be replaced. Most newer air conditioners don’t have motor belts, so you’re more likely to hear this sound in an older system. If you hear squealing in a newer unit, it could be an issue with the bearings on the condenser fan motor, which could signal that you need a new motor.

Banging Sound

If a piece of the air conditioner is missing, it can cause a banging sound in the unit. In many cases, banging comes from a loose rod or piston pin in the condenser. To fix the strange noise, replace the loose or missing part.

Humming Sound

Many air conditioners make a low humming sound when they run, which is usually normal. However, if the humming sound is louder than usual or uneven, it could signal an issue with the AC unit. Loose parts or piping can lead to vibration and humming. This typically isn’t a very serious issue, but it can lead to larger problems if it isn’t addressed.

Hissing Sound

The most likely reason for a loud hissing sound is a refrigerant leak. Refrigerant is the liquid that cools the air and is one of the most important parts of the entire system. A hissing sound is often accompanied by an air conditioner that isn’t working efficiently or cooling the air. Refrigerant leaks are likely due to skipping routine maintenance and should only be fixed by an HVAC professional.

Hearing AC making strange noises

Rattling Sound

The more an air conditioner runs, the looser its parts naturally get. A rattling sound likely signals that the pieces are wearing down and getting looser. Rattling often happens when the fan gets loose. Another possible scenario is that there is debris in the AC unit, such as old leaves or twigs. An HVAC technician can perform an inspection and tighten the pieces and clean the machine to stop the rattling.

Buzzing Sound

A buzzing sound can come from a number of areas in an air conditioner, but it likely means the same thing: something is loose or missing. If a piece gets loose or falls off, it causes the other parts of the air conditioner to work harder, which can put things into overdrive and lead to a buzzing sound. Because a buzzing sound can be from so many different things, your best course of action is to call an HVAC technician for an inspection of the entire system.

Whistling Sound

A loud whistling sound could signal an issue with the ductwork. Air escaping the system or going to places it shouldn’t can often create a whistling noise. Whistling is more likely to occur in air conditioners that have dirty filters or old ductwork. Houses that have replaced parts of their ductwork over time could also be more prone to a whistling AC unit if the pieces aren’t connected properly.

If your air conditioner is making a funny noise, don’t just sit back and wait for it to fix itself. Start by troubleshooting air conditioning and then take proactive steps to call a professional to look at the unit before that strange sound leads to a larger problem.

Aside from making strange sounds, your air conditioner may not be working for a variety of other issues that require troubleshooting air conditioning.

5 Reasons Your AC Might Not Be Working


Your air conditioner is one of the most important parts of your home, especially during those hot summer months. However, things can quickly go downhill if your AC isn’t cooling properly. You may need residential AC repair in Longmont to solve your problem and get your house back to a comfortable temperature. Here are five common reasons your AC might not be cooling properly.

1. The Filter Needs to be Changed

Air from the AC unit passes through the air filter, and a dirty filter can make it difficult for cold air to get through. Your AC unit has to work a lot harder to push air through a dirty filter, which can lower its power and raise your energy bill. Change your filter at least every 3 months to allow the air to move efficiently. If you have pets or run your HVAC system constantly, you should check your filter even more frequently.

2. The Vents Are Blocked

Sometimes increasing the strength and effectiveness of your AC is as simple as cleaning the house. Vents are what determines how much cool air enters a room. If they are blocked by furniture or other items in the room, the air doesn’t have anywhere to go. Vents can also cause problems if they are full of dust or debris that naturally accumulates in a home. Clean around your vents regularly. Consider hiring a professional to clean your ductwork as needed.

3. Cool Air Is Seeping through the Insulation

Insulation works to keep cool air inside the house and block out warm air from outside. Powerful sun rays beat down on the roof throughout the summer, which means insulation in the attic or crawl space is important to cooling the entire house. Proper insulation helps more cool air from the AC stay inside the house instead of losing it all through the walls or roof. Older houses may have thinner insulation, or it could have fallen down over time. For best results, your attic or crawl space should have thick, energy-efficient insulation around the entire roofline, wall joists, and floor. Walk around your attic to see if the insulation needs to be replaced or repaired.

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4. The Thermostat Is Outdated

The AC unit does all the work, but the thermostat tells it what to do. As you update and replace your HVAC system, you should also update and replace the thermostat. One of the first steps to checking on your AC unit is to make sure the thermostat is set to cool at a temperature that’s lower than the temperature outside. Older thermostats may give out and cause the system to be faulty, even if the HVAC system itself is still in good condition. If that’s the case, look for a modern, programmable thermostat that allows you to set different temperatures for different times of the day. Smart thermostats work with other sensors in the home to automatically adjust the temperature based on the weather and occupancy of the house. Replacing a thermostat is significantly less expensive than replacing an AC unit.

5. The Machine Is Broken or Leaking

There are a number of components that allow AC to create and blow cool air. If one of those parts is damaged or has a leak, it can hurt the entire system. Refrigerant is the liquid that keeps the air cool as it cycles through the system. If the refrigerant levels are low, it likely means there’s a leak that needs to be repaired by a professional. Condenser coils also help produce cold air, but a blown fuse can make the AC unit appear to be working normally even if no cool air is coming out.

If your AC isn’t cooling properly, make sure the filter is clean and the vents are open, and then call an HVAC professional for inspection and repairs.

Sometimes troubleshooting residential air conditioning isn’t enough and the unit needs to be replaced. These guidelines will help you know when your AC issues are big enough to need a replacement unit.

Four Ways to Know You Need to Replace Your Air Conditioner

Summer is right around the corner and soon you’ll be counting on your air conditioner unit to keep your home cool and comfortable. As temperatures continue to rise outside, you want to be confident that your AC will be able to handle the heat. Regular maintenance can help get your air conditioner ready, but if you have an older unit, it may be time to look into air conditioner replacement.

If you suspect that your AC may be on its last leg and it’s probably time to replace your air conditioner, here are four ways to know or key signs to watch for that might tell you that you are right.

1. There Is a Lack of Cool Air and Low Airflow Coming From the Vents

The most obvious sign of a problem with your air conditioner is a lack of cold air coming from the vents, even after you’ve turned the thermostat down. This could be from a number of reasons such as low refrigerant levels or a damaged condenser, but it could also be an indication that your AC is not able to work effectively.

Low airflow is another obvious sign that something is wrong. Take a moment to go through your house and inspect the airflow from individual vents. If you notice that airflow is only weak in certain areas of the home, your problem might simply be from clogged vents or obstructed ductwork. A broken thermostat could also be to blame if airflow and temperature are only affected in certain areas of the house. However, if you find that airflow is low throughout the entire house, there is a good chance that the unit’s compressor and other possible components are failing.

2. There Is an Accumulation of Moisture Around the Unit

Some amount of condensation around an air conditioner is normal, but only to a certain extent. If you’ve noticed a buildup of moisture or have identified a leak in your air conditioning unit, you should make sure to have that inspected as soon as possible. Extra or excessive moisture could be a sign of a clogged condensate drain or a refrigerant leak. Refrigerant can be extremely harmful to the health of you and your loved ones and should be addressed as quickly as possible. Moisture build-up can be a sign that your AC unit is not able to function properly and it can also increase the risk for water damage or mold growth.

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3. There Are Foul Smells and Strange Sounds Coming From the Unit

Using your senses is a good way to gauge how your air conditioner is operating. There shouldn’t be strange smells or sounds coming from your air conditioner when it is running. If you smell anything foul, pungent, musty, burning or smoky, there is something surely wrong with the unit. It could be that the wire insulation has burned out or that mold is growing within the unit or ductwork. A properly functioning air conditioner should not be loud or noisy either. If you hear grinding, squeaking, banging, or rattling noises, there is likely a serious problem that should be addressed before it becomes worse.

4. You Are Spending More Money Than You Should Be

If you think your air conditioning unit is functioning poorly, you might simply take a look at your energy bills and check if they are higher than normal. Air conditioners that are not operating efficiently will be forced to work much harder to cool your home, costing you a significant amount on your monthly energy bills.

You might also consider the number of repairs and service calls you’ve had to pay for due to problems with your AC unit. There reaches a point where you will spend more on repairs than you would if you were to replace the entire unit.This may help you decide if you should repair or replace your air conditioner: https://bit.ly/2DbCltJ

Is It Time to Replace Your Air Conditioner?

Making the decision to replace an air conditioner can be a difficult one. AC units are expensive, but there are times when it becomes more cost-effective to invest in a new unit rather than continue repairing an old one. You can read more about the average cost of installing a new air conditioning unit in this article by Homeadvisor.com.

A new, high-quality air conditioner can improve the comfort of your home while maintaining reasonable electricity bills. At Stone Heating & Air, we specialize in providing quality air conditioning services for the Longmont community, including sales and installation of new AC units. We offer a variety of high-efficiency units that will meet the needs of your home and keep you cool during the hot summer months. Contact us today to learn more.