HVAC Repair Tips


Air conditioners make the noise of low, steady air blowing noise when they function. However, if your HVAC system is making loud noises or the noises are low but completely weird like a low whistling sound, then you should inspect the AC to find the cause of the issue. Air conditioning repair services can fix these problems in a better way, but the kind of sound the AC makes can hint at the problem that you need to fix. Let’s learn!

Clicking Sound

Your air conditioner makes a clicking sound at the start and end of each cooling cycle. This is normal for an AC. However, if your AC keeps making a clicking sound repeatedly or at times other than the start and end of a cooling cycle, it could be due to these reasons:

Faulty Thermostat

Thermostats have a relay that sends power to the AC when it has turned on the AC. This relay makes a clicking sound. If the relay is broken or there are loose wires, the relay keeps trying to send power to the AC and fails. During this, you will hear a continuous sound.

Dead Capacitor

A capacitor in an AC acts as a battery and helps the AC start up the cooling process at the beginning of every cooling cycle. It’s present inside the outdoor unit of your AC.

When the capacitor loses its charge with usage, it becomes unable in giving the required power to the AC for cooling the house. So, your AC starts making clicking noises because it can’t receive power to start the cycle. Moreover, if your AC capacitor is dyeing, you may also hear a consistent humming noise from the side of your AC’s outdoor unit.

Malfunctioning Contactor

A contactor is part of an AC that receives the signal from the thermostat to start or stop the compressor. But when the contactor is bad, it won’t give the go-ahead signal from the thermostat to the compressor. In turn, the AC won’t turn on or cool and make clicking noises.

If you want to ensure that the contactor is bad, get near the outdoor unit. It may be sounding like humming, buzzing, or chattering. Hire an expert at this point to fix the problem.

Hissing Sound

If you’re hearing a hissing sound coming from your AC, look for these issues:

Refrigerant Leak

A common cause of a hissing sound in air conditioners is leaking refrigerant. The hissing is the refrigerant leaking from tiny holes in coils or damage to the refrigerant line. Both of these parts of AC deteriorate over time and can corrode or sustain damage which results in small holes that leak refrigerant out. You may hear this sound even the AC is turned off. Consult an expert who can fix the leaks and refill the refrigerant.

High Compressor Pressure

Air conditioners have a compressor that pushes the refrigerant to travel inside the coils. If the compressor has a leak or too much pressure builds inside it, it will lead to a hissing sound. You should turn off your AC right away and contact an AC technician.

Many modern air conditioners have a safety feature that turns off the AC automatically if too much pressure is built by the compressor. So, you won’t hear the hissing sound because the AC will be turned off by itself.

Screeching Sound

This sound is probably the most irritating and easily recognizable. Find out the causes of your AC making screeching or squealing noises.

Broken Fan Belt

The fan and motor use a belt that enables the functionality of the fan in ducted air conditioning systems. With usage, this belt can wear out or break. This leads to a screeching or squealing noise. Moreover, sometimes, the belt is affected by the high temperature and contracts and expands. This affects its functionality and creates noises. Repair or replace the fan belt.

Damaged Bearings Of The Fan

As older HVAC units use a fan belt, newer units employ a direct drive motor for the functioning of the condenser fan. Bearings are used for the fan to work. So, if you have a newer HVAC unit and hear a squealing or screeching noise, it may be the damaged bearings of the condenser fan.

You should turn off your air conditioner immediately because if you keep the air conditioner running and ignore the issue, it can damage the fan motor. This will become a more expensive replacement for you so have the bearings replaced or repaired by a certified AC repair technician when you hear screeching noises.

High Compressor Pressure

We have explained in the earlier point that high pressure created by a malfunctioning AC compressor leads to problems. You may hear a hissing, screeching, or squealing sound coming from the condenser unit. You should turn off your AC and call an expert.

Banging Or Rattling Sound

Clogged And Dirty Condenser Unit

The cause of the banging or rattling noise of your AC could be a minor problem like a clogged condenser unit. As the condenser unit is located outside, dust, debris, leaves, and shrubs can block it so much that the unit can’t operate properly. This is more likely if your outdoor unit is placed near trees, shrubs, and landscapes.

The fix is rather easy. Remove the cover of the condenser unit and remove the items you can see. Then, thoroughly clean the unit. You can also get professional help for this.

Misaligned Fan Blades

With usage, the fan blades installed in the condenser unit can become misaligned. With it, they strike other parts near them which causes a banging sound. Try to fix this issue as soon as possible because delaying it can affect other parts of your AC as well.

Loose Screws

This is a rather simple cause of a rattling sound. Screws are used to keep different parts of the unit in place. Over time, the screws can become loose or fall out. The parts that become free of screws produce a rattling sound as the AC functions.

Inspect all the components of the AC and if the screws are loose or lost, replace the screws to stop the rattling noise.

Bubbling Sound

Refrigerant Lines Issue

A bubbling or gurgling sound coming from an AC can be due to the improper sealing of refrigerant lines. This is because air become strapped in the refrigerant lines. However, keep in mind that a refrigerant leak can also sound like a bubbling sound apart from the common hissing sound. Get an expert to seal the refrigerant lines and also check the lines and coils for leaks.

Blocked Drain Line

If the AC is producing excessive moisture, it can cause clogs in the drain line. Due to the excess of moisture, water will make a gurgling sound.

Other than that, your AC can make a bubbling or gurgling sound if the condensate pump malfunctions. The pumps become unable to remove water properly from the drain line and the excess water produces the bubbling noise.


We have covered different types of noises air conditioners can make that hint at the problem they are having. To avoid complications, get the services of HVAC repair services McLean to detect the sound and its cause to fix the issue.


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