My Air Conditioner Sounds Like a Jet Engine - What could be wrong?

If your air conditioner sounds like a jet engine, something is clearly wrong. It is normal for your air conditioner to make some noises; thermostats click at the beginning and end of cooling cycles, and condenser fans produce a humming noise. But some air conditioner sounds indicate minor to severe problems.

A jet engine noise is one problematic sound that could indicate several possible issues, as does buzzing, squealing, and hissing sounds. These abnormal sounds don’t automatically require a visit from an HVAC technician. You may be able to diagnose and resolve the problem on your own. Issues that aren’t dealt with can lead to major problems and expensive repairs down the line.

Common Reasons Why Your Air Conditioner Sounds Like a Jet Engine

If your air conditioner sounds like a jet engine, this is a sure sign that it is breaking down. The problem could be a faulty condenser fan, a failing compressor, or frozen evaporator coils.

A Faulty Condenser Fan

A jet engine sound may be produced if the condenser fan in the outdoor unit is working improperly. The noise may indicate an accumulation of dirt and debris within the unit or an electrical issue with the fan.

A Failing Compressor

A jet engine noise may indicate a mechanical or electrical issue with the compressor, such as a faulty relay switch delivering improper amperage.

Frozen Evaporator Coils

Evaporator coils within the indoor unit may produce jet engine noises if they accumulate ice and freeze up. Coils may freeze due to a refrigerant leak, lack of air circulation, faulty refrigerant lines, or a broken expansion valve.

outdoor air conditioner unit on concrete slab surrounded by foliage and brick wall
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Other Air Conditioner Sounds You Shouldn’t Ignore

While your air conditioner should make some noise, this doesn't mean that it should make loud or concerning noises. Whether it's a faint clicking in the night, a constant buzzing, or a sudden high-pitched squeal, your air conditioner's loud and disruptive sound could indicate moderate to severe issues.

Running Water

The sound of running water indicates an issue with refrigerant flow through the system. Ignoring this sound will likely lead to a breakdown. A bubbling or gurgling sound indicates excess moisture due to a blockage, crack, or hole in the drainage line.


A clattering sound may indicate the fan blades are loose or the fan is unbalanced and needs to be reset by an HVAC technician.


A buzzing sound may indicate several issues, some of which are severe. Dirty condenser coils can produce a buzzing sound. A handy homeowner should be able to remedy the situation by cleaning the coils. More severe issues like loose or unbalanced fan blades or a faulty fan motor will require the help of an HVAC technician. Loose metal components touching each other or with an electric current running through them may also buzz. The most serious problem would be a refrigerant leak, which requires immediate attention from an HVAC technician.


A squealing or screeching sound may indicate fan or fan belt issues. The fan motor’s bearings may be bad, or the belt may need to be replaced. A high-pitched squealing or screaming noise may indicate the compressor is operating at an exceptionally high level of pressure, a very serious problem. The sound may be coming from the compressor itself, or it may be an alarm warning of the dangerous situation and the system shutting down.

Humming and Clicking

A constant humming noise can be produced if something is lodged inside the condenser unit. The vibrations from the unit may cause the foreign object to vibrate and hum. Leaves, branches, and other debris that slip into the unit can easily be removed.

Humming may also indicate that the fan is impaired or the contactor relay switch is faulty. The switch is responsible for starting the condenser after receiving a signal from the thermostat. Using the air conditioner with a defective contactor relay switch could severely damage the unit.

A constant clicking noise indicates an electrical issue like a defective thermostat or control interface or an issue with the capacitor or compressor. Electrical problems that are not dealt with can cause significant damage to the unit.


Hissing from inside the home can indicate minor issues such as a duct leak or an incompatible air filter. Hissing from the condenser unit suggests a more serious problem, such as a faulty HVAC compressor, a malfunctioning expansion valve, or a refrigerant leak.

Troubleshooting Air Conditioner Sounds

You don't always need to call a professional immediately for HVAC system repairs. You should first investigate the unit when you hear an unusual sound from your air conditioner, as many problems have DIY simple solutions.

man spraying hose to clean outdoor air conditioner unit

1. Clean your outdoor AC unit

The outdoor air conditioner unit is vulnerable to the elements in its immediate environment. Leaves, dirt, and other debris may get inside through the slits. For your safety, turn off the unit before removing the cover. Remove the top grill, grab loose debris, and spray it off with a hose. Once clean, be sure to close it back up.

closeup of central air conditioner unit outdoor fan

2. Check the outdoor fan and inspect the unit

When your air conditioner switches on, both the exterior and interior components are exposed to vibration. As time goes on, the shaking may cause parts to loosen. In most cases, you can remove the top of your outdoor air conditioning unit with a screwdriver and closely inspect the condenser fans: loose parts, especially in motion, are usually easy to spot.

iced frozen air conditioner HVAC system evaporator coil

3. Inspect the coils

If your air conditioner evaporator or condenser coil is frozen or dirty, that could be causing the jet engine sounds. Try cleaning your coils regularly to remove dust and debris and prevent frost. If you see ice-build up, turn off the power and let the unit completely dry before turning it on again.

central air conditioner system copper refrigerant lines

4. Check the refrigerant lines

When the copper refrigerant lines rub against something like a nearby wall, that can create a jet engine-like noise. The refrigerant lines should never be rubbing against anything. To prevent friction and reduce disruptive noises, you can add rubber insulation to protect the tubes against direct contact with a wall or nearby structure. If possible, it's best to avoid any potential metal-on-metal exposure.

HVAC professional repairing outdoor air conditioner unit

5. Call an HVAC professional

Homeowners can do a lot to prevent air conditioner issues and stop concerning noise problems. However, there are limits to what an untrained person can do themselves. If you still hear an unusual sound, it is advisable to turn the entire system off and call an HVAC technician for assistance.

Powering down the unit is a fundamental precautionary measure. If the air conditioner unit is not functioning correctly, keeping it running could damage it further and be more expensive than if you had just stopped it after the initial problem started.

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If your air conditioning is suddenly producing a sound that grabs your attention, it is likely that there is an issue with the unit. Jet engine, running water, and clattering sounds are abnormal. Some homeowners may choose to investigate the sounds and take steps to eliminate them, such as cleaning the outdoor unit. If trouble-shooting measures do not resolve the issue, or if a homeowner is uncomfortable undertaking such actions, the unit should be powered down until it is inspected by an HVAC technician to avoid further damage.

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1 comment

Olivia Smart

Olivia Smart

Thank you for explaining that a squealing sound could be a fan or belt issue. My mom’s AC has been making a lot of weird noises this last week. I’ll have to share this with her so she can make sure to get this checked out and fixed soon.

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