Why the Air Conditioner Makes a Loud Noise When Starting?

Why the air conditioner makes a loud noise
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Air conditioners make noise when starting, which is a normal thing in the air conditioner. However, the air conditioner makes loud noise indicating that the parts in the system are faulty.

The faulty parts need replacement or repair to help reduce the noises in a room. Some kinds of noises are not conducive for the ears. Read the article to know the causes and steps to fix them.

Reasons why the air conditioner makes a loud noise when starting

air conditioner makes loud noise when starting

Availability of dirt in the air conditioner

Dirty particles like dust, tree branches, leaves, and other dirty particles may stick into the air conditioner. The dirty particles then accumulate into the air conditioner, blocking it and causing some banging and rattling noise in the air conditioner.

Baggy and free screws

Baggy screws make a loud noise in the air conditioner when starting because the screws vibrate when turning on the air conditioner. The sudden vibration every time the air conditioners turn on makes the screws loose after some time.

Issues with the fan and the compressor

The air conditioner makes a loud noise when starting if there are issues with the compressor and fan. Also, the air condenser produces a banging noise when the fan motor or compressor breaks in use. The problems with the compressor and fan maybe because they are ancient. The compressor may also have leaks that produce some noise since the compressor has valves in charge of the pressure of the refrigerant.

Faulty connector belt

A connector belt connects the fan motor and the fan. Therefore a faulty belt causes squealing noise since the belt expands and contracts due to the changes in the temperature and humidity levels, making them wear over time.

Excessive pressure of air in the conditioner

When the pressure in the air conditioner becomes excess, it causes noise in the air conditioner since some explosions occur inside the compressor.

Presence of leaks in the refrigerant

Leaks in the refrigerant make the air conditioner produce a loud noise when starting because it lowers the refrigerant level.

Free and loose air filters

When the air filters are loose, the air conditioner produces a loud noise when starting because the air passes through the air filters, and if there are some loose parts, the air will pass through these parts, producing some noise.

Lose of charge in the capacitor

The capacitor is the device that stores power to start the compressor, so when the capacitor loses its charge, it cannot power on the compressor making the air conditioner make a loud noise when starting.

Faulty electrical connectors

Faulty electrical connectors like the signals and sockets may affect the air conditioner when starting, making it produce loud noise since the connectors will keep switching off and on, producing some noise. In addition, deficient electrical components can cause some sparks when starting the air conditioner where noise accompanies these sparks.

Defective thermostats

Defective thermostats result from using the thermostat for long, making them have a poor connection to the air conditioner. The loud noise after that results from the relay, which keeps sending power to the faulty thermostat.

Leaking duct in the air conditioner

When the air conditioner has leaking ducts, air will pass through the leaking ducts making the air conditioner produce a loud noise.

Dirty air filters

Dirty air filters block the exit and entrance of air into the air conditioner, making the motor produce loud noise since air forces itself into the air conditioner, which comes with high pressure. In addition, the air conditioner’s force to create a path into the air conditioner makes noise in the air conditioner.

Lack of lubrication in the motor

Some motors need lubrication more frequently for fast and easy running. Therefore, when such engines lack lubrication, it will produce noise at the start, making the air conditioner have loud noise when starting if the lubrication process fails to occur.

Faulty contactor

A contactor is a tool that regulates the connection between the air conditioning system and the power suppliers in a room. So when the contactor is faulty, it fails to perform its work by turning off or on the power supply. Instead, it forces the air conditioner to turn on the electricity itself, producing a loud noise.

Faulty capacitor

A capacitor is a device in the air conditioning system that stores power for use by the air conditioner. Therefore when the capacitor is loose or faulty, it prevents some parts like the fan from switching on, causing some noise due to friction.

Read More: Air conditioning capacitor Makes noise How to fix

Poor connection of wires

When the connection of wires is loose, some cables may not have a cover to wrap them and tend to be flexible at some point. These flexible wires may produce some noise when the air conditioner starts because of vibrations in the system.

Freezing of the air conditioner

The air conditioner makes a loud noise when starting due to freezing as it blocks the exchange of air in a room, forcing the air conditioner to strain. In addition, the air conditioner may freeze due to effects from the thermostat and the refrigerant.

Types of noises the air conditioner can make when starting

Types of noises the air conditioner can make when starting

1) Banging

Banging in the air conditioner mainly occurs when there are some issues with the components in the air conditioner in that some parts are loose or the compressor is old enough for use.

2) Clacking

Clacking occurs when the parts in the air conditioner lack balance such that they knock against each other when the air conditioner starts due to the vibrations. It results from the looseness of the air conditioning system components.

3) Clicking

Clicking noise results due to the operations with the electrical appliances in the air conditioner. Continuous clicking then causes loud noise in the air conditioner when starting.

4) Buzzing

Buzzing is the most common noise in the air conditioner since it results from operations. When you hear a buzzing noise, that means your air conditioner has loose parts, dirty air filters, leaking refrigerant, faulty fan and thermostats, loose wires, and dirty condenser coils.

5) Squealing

Squealing results from the faulty motor. Although it is a typical sound, it sometimes leads to loud noise in the air condenser.                

6) Humming

Humming is a typical sound, but when the air conditioner hums and fails to start, there might be issues with it, like the loose wires or the refrigerant may have some problems.

7) Rattling

When the air conditioner becomes very old, it will start to rattle when turning on. Rattling starts because its part will be old enough that it does not need replacement.

8) Screaming

Screaming is the most severe problem that only professionals can fix because of refrigerant and compressor issues.

9) Pulsating

Pulsating noise shows that the air conditioning system needs some replacement since it’s a typical sound, but the air conditioner has problems when it turns out to be loud.

10) Whirring

Whirring is an airplane-like sound that occurs due to reasons like a faulty fan that whirrs or rather dirty particles like leaves that accumulate inside the air conditioner such that when air passes through some ducts, the papers do whirr.

How to fix loud noise from the air conditioner

How to Fix Loud Noise From The Air Conditioner
  • Replace old air conditioning components like the condenser, compressor, and air filters. Consult a technician to help in the replacement process to avoid damaging the air conditioner.
  • Align the condenser coils in the air conditioner by making them straight to prevent the occurrence of the loud noise
  • Fix the loose wires to ensure they are tight so that when the air conditioner vibrates, they do not come in contact with each other.
  • Clean the dirty air filters that block air into the air conditioner by removing tree branches, leaves, and dust particles.
  • Lubricate the air conditioning system to avoid rust which makes the motor produce screeching sounds.


The article shows why the air conditioner makes noise when starting and how to fix the noise in the air conditioner. Please read the article carefully to cite the exact causes of noise in your air conditioner and follow the solutions to fix them.

Remember to read the manufacturer’s instructions on the air conditioner parts and contact a technician to replace the condensers and air filters.

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