If your AC unit is making pulsating sounds, you’re probably concerned something is wrong with it. However, it doesn’t always mean it has a serious issue. Still, you should investigate any abnormal sounds to keep it running efficiently. Typically, air conditioners make pulsating sounds if the filter is clogged, the fans are unbalanced, or if the motors are straining. This guide explores the common pulsating noise causes, how to fix them, and when to call an HVAC pro for help.
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Is a Pulsating Noise in My Air Conditioner Normal?
Any loud noise coming from your air conditioner at startup and when it is running — whether it’s pulsating, squealing, clanking, a humming noise, or a buzzing noise — can be a cause for alarm.
So, when it comes to a pulsating noise specifically, how worried should you be? The answer won’t surprise you. It could be no big deal and a quick fix, or it could be a very big deal.
But does that sound normal? Nope. A pulsating noise is not normal for an air conditioner and should be looked at and fixed sooner rather than later.
What Could Be Causing the Pulsating Noise in my Air Conditioner?
A pulsating noise in your air conditioner or heat pump can be caused by a variety of factors, ranging from minor issues to more serious problems. Here are the most common culprits behind this annoying sound.
Plastic Outdoor Unit Pad
If your outdoor AC unit is sitting on a plastic pad, the vibrations from the compressor can cause the pad to resonate and create a pulsating noise. Adding a sound-dampening material between the unit and the pad can help reduce this noise. Alternatively, you can have a local contractor pour a concrete pad for your air conditioner to eliminate the noise entirely.
Air Handler Not Balanced on Basement Floor
If your air handler is located in the basement and is not properly balanced on the floor, it can cause vibrations and a pulsating noise. Check it with a bubble level. If it is unlevel, add rubber anti-vibration pads under it to get it level.
Dirty Air Filter
A clogged air filter will reduce or block airflow from the blower motor. This will cause the system to strain and could lead to a pulsating noise. You should check your air filter every month and replace it when it is dirty – about every 3–6 months, depending on the type of filter.
Blower Fan Out of Balance
If the blower fan in your air handler (indoor unit) is out of balance, it can cause a pulsating noise as it rotates. This is often due to a buildup of dirt and debris on the fan blades or loose parts, which can throw off the balance and create vibrations down your ductwork. To clean the fan, turn off the power to the AC unit (don’t just turn your thermostat off; flip the breaker) and use a vacuum with a soft brush attachment to clean it.
Condenser Fan Out of Balance
Similar to the blower fan, an out-of-balance condenser fan can also cause a pulsating noise. The condenser fan is located in the outdoor unit and is responsible for releasing heat from the refrigerant. It can build up with dirt and debris over time – you can use a shop vacuum to clean it off. In some cases, the fan can get damaged from debris falling into it. If this is the cause of the pulsating noise, an HVAC technician may need to replace the fan.
Bad Fan Motor Bearings in Condenser
Over time, the bearings in the condenser fan motor can wear out, leading to a pulsating or humming noise. During regular HVAC maintenance, the contractor will lubricate these parts. However, if left unchecked, this can cause the motor to overheat and fail, resulting in a more costly repair.
Low Refrigerant Levels
If your AC system is low on refrigerant, it can cause the compressor to work harder, potentially leading to a pulsating noise. Air conditioning units are closed-loop systems, so low refrigerant levels are always caused by leaks. So, you’ll need an HVAC professional to inspect it, fix the leaks, and recharge the refrigerant.
Dirty Condenser
A dirty condenser (outdoor unit) can restrict airflow and cause your AC system to work harder, potentially leading to a pulsating noise. Regular maintenance, including cleaning the condenser coils of outdoor debris like leaves, twigs, dirt, grass clipping, etc., can help prevent this issue.
Can I Fix a Pulsating Noise on my Air Conditioner, or Should I Call an HVAC Repair Pro?
You can definitely save some money in the short run by fixing smaller problems yourself. But for bigger issues, it might take a trained HVAC technician to take care of the problem. For instance, with the refrigerant line, you might be able to take care of it yourself, but if getting into walls sounds daunting, you might want to leave it to a pro. The vibration might be causing enough friction to create a refrigerant leak, which is also a matter you should leave to the professionals.
Final Thoughts on a Pulsating Noise in Your Air Conditioning
The good news is that a pulsating noise is often a very simple DIY fix, like tightening up a loose coil fan or fan blade or even putting some sound-reducing material between the heat pump or AC unit and the plastic pad it sits on. And even if it is something more serious, it is nothing your HVAC technician has not dealt with before. Keeping your HVAC system clean and well-maintained can go a long way in preventing these kinds of noises from happening in the first place.
Knowledge is power – knowing that pulsating noise is annoying but easily fixable can help you manage the problem and get on to more important things!
Frequently Asked Questions
You can fix some causes yourself, such as a dirty air filter or clogged condenser unit. However, you should hire an HVAC technician for more complex issues like a faulty fan motor or a refrigerant leak.
The pulsating noise from your air conditioing system is likely serious if you also have weird smells, poor cooling performance, low air flow, and other unusual symptoms.
Yes, even the small problems – like a dirty air filter – puts additional strain on your AC unit, which leads to more stain. This can cause a more expensive breakdown later.
