Why Does My AC Make A Clicking Noise & What To Do?

Air conditioners these days are relatively quiet. Under normal circumstances, it can only make a low, steady blowing noise. If you notice your air conditioner making a clicking noise, it could be a sign of a serious problem.

In general, a clicking noise in your air conditioner could be caused by a bent fan blade, some loose parts, a damaged contactor, or a dead capacitor.

In this post, I will examine various types of clicking noises in an air conditioner and advise you on how to deal with them effectively.

I understand how difficult it is to understand AC issues, so I will do my best to explain them as simply as possible.

A soft clicking noise when your AC is turning on or off

If your air conditioner only makes a clicking noise when it starts up or tries to turn off, there is no need to be concerned.

This sound occurs when the thermostat attempts to send signals to your air conditioner, and the relay opens to charge your unit. When the signal is received, your AC will turn on.


It is a normal sound that indicates that the thermostat is sending commands to your air conditioner. You will quickly become accustomed to this sound.

AC clicks but doesn’t start 

ac clicks but doesn't start

However, if you hear the click but your air conditioner does not turn on, this indicates that something is wrong. A faulty capacity, contactor, or thermostat is usually to blame. Let’s discuss these three components one by one.

A damaged capacitor

Some air conditioning systems require more power to start than they do to run. The capacitor functions similarly to a large battery to provide the extra power your AC requires.

When it is worn out or malfunctioning, your air conditioner will not be able to turn on. When your air conditioner is attempting to activate, you will hear a clicking noise from the outdoor unit.

A faulty thermostat

While a soft click from the thermostat is normal, you should exercise caution if the clicking sound becomes loud. Perhaps the relay or wiring has failed.

The relay switch will constantly try to send power to your outdoor unit, making constant noise, but your AC will not turn on.

A failed contactor

The contactor is not easily broken, but it can. The contactor will receive the command from the thermostat and allow power to flow through it to turn on your air conditioner. When it fails, the outdoor unit cannot receive current and thus does not turn on.


If any of these components fail, I recommend contacting a certified HVAC expert. They will detect the problem and determine whether these parts need to be repaired or replaced.

You can also try to replace them on your own if you have the necessary expertise and want to take risks. Remember to turn off the power supply in advance.

Constant AC clicking when the machine is on 

When your air conditioner is on, you may hear a clicking sound. This sound gives you the impression that your air conditioner is about to fail, which is terrible. The loose screws and nuts, as well as the fan, are frequently to blame.

Loose parts

You can’t avoid the deterioration and wear of your air conditioner’s components over time. If the compressor’s screws, nuts, and tubes become loose, it will begin to make a constant noise. Another reason for the clicking sound in the outdoor unit.


You can contact an HVAC professional or tighten these parts with a nut driver or ratchet wrench.

Fan obstruction or loose fan blades

When the fan blades repeatedly strike, a clicking noise is produced. Due to accumulated dirt and dust on the blower motor or loose parts, the fan blades can be bent, blocked, or imbalanced. 


If the problem is caused by a dirty motor or blades, you can resolve it by removing the buildups. You could also try tightening the parts yourself. If it doesn’t work, consult an HVAC professional.

Air conditioner makes a clicking noise when off

When you turn off the machine, you may hear a clicking sound. It could be due to the metal ducts expanding and contracting. When you turn off the machine, the temperature and pressure inside the ducts change dramatically, causing a clicking noise.


It is a natural physical phenomenon. You have no control over the situation.


The clicking noise coming from your air conditioner can be both annoying and indicative of a variety of problems.

If the clicking noise is soft and only occurs when you turn your air conditioner on and off, it is simply a normal sound caused by the movement of the relay switch or the expansion and contraction of metal ducts.

When the clicking noise is repeated and coming from the outdoor unit, it could be caused by fan blades striking the case or loose screws and nuts vibrating. In this case, your air conditioner should be able to keep cooling your room.

If your air conditioner does not turn on with the clicking nose, there is a problem with the relay switch, thermostat, or capacitor.

About The Author

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Liz Yang is the founder of Airsmartly. She has been working at home for a few years and realizes that the performance of the HVAC system plays such an important role in our life. She has tested dozens of products in person, like humidifiers, air purifiers, dehumidifiers, and ACs, and wants to share tips about using or troubleshooting these products with you. Her uncle is an HVAC expert with over 30 years of experience in the field, and often offers assistance when she is unsure how to handle a situation. He is also in charge of reviewing the articles on this site.

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