Why does the car AC make noise when it’s turned on?

As summers get hotter, the air conditioning system presents a lot more interest, especially for your car. And, being a fairly complicated mechanism, the car’s AC is prone to have a lot of problems. 

One important factor to consider is the noise produced by the car air conditioning system when it is turned on. This symptom can give you a heads up that your car AC has a problem but that noise doesn’t also mean that there is clearly an issue with it.

The most common causes why your car’s AC makes noise when it is turned on are :

  • The AC compressor needs to be changed 
  • The condenser fan needs to be replaced 
  • The evaporator core needs to be cleaned 
  • The evaporator coil should be replaced 
  • The air filter in the AC system should be replaced.

To check these factors, it is possible that you need to make a full diagnostic test of your car’s air conditioning. This is something that a professional automotive technician can do for you at your home or the shop of your choice. 

What problems does the car AC compressor have?

When car air conditioning is making noise when turned on it indicates that there is some problem with the AC compressor. The compressor is the heart of your AC system, so most likely it is also the cause for a lot of other problems as well. 

The compressor is, usually, responsible, in more cases, for the bad sound symptoms that cause the air conditioning system to fail.

One of these problems is the lubrication of the compressor. In many situations, there is not enough lubricant circulating through the compressor and it doesn’t move as freely as it should.

If the air conditioning compressor noise is heard even after it is turned off, this means that there is definitely a problem with the compressor’s drive pulley bearing. Because of this that an unusual hum appears, and a complete failure of the bearing is not far off. This will also include other consequences, such as a broken pulley. 

Due to a bad bearing, the coupling coil can burn out, which will lead to refrigerant leaks. So, having heard suspicious sounds coming from under the hood and after turning off the AC system, you should check that bearing. 

Another factor to consider is the voltage that your car’s AC gets from its battery. The voltage threshold of your system (the highest voltage it can accept) is higher than what is needed to work properly, therefore in some cases, when the air conditioning system gets a little too high for its own good, the compressor can be damaged.

If you turn on the air conditioning system, and you do not hear the characteristic click when the electromagnetic clutch engages with the rotor shaft. The problem may lie in the lack of the required pressure of the refrigerant in the system (less often its excess). The pressure control sensor reacts to such abnormal situations by switching off the compressor.

As a side note: It is very common for an air conditioning system to be making noise when you turn on your car’s AC. The usual noises are clicking sound immediately after turning the AC on that indicates the compressor has just started.

Another “common” sound is when you have the impression that you have two working motors on your car, one produced by your engine and one produced by your compressor. A difference will be that the compressor will work intermittently, a few seconds and after that, it will stop and will turn on later on.

What problems does the car AC condenser fan have?

The condenser fan is responsible for pushing out warm air from the car’s AC system to the outside to create a cold environment inside. The condenser is usually located on the front or back of the car near the engine.

The problem with the condenser fan is that it will allow heat and humidity into your AC, making it less effective to cool your vehicle, causing it to emit different sounds when you turn your AC on

Why does the car AC evaporator get dirty?

The system of the car air conditioning is very complex. The evaporator is responsible for cooling down your car’s interior. It’s fairly simple to clean and maintain; however, if you do not do it correctly, problems might be generated inside your vehicle.

It usually gets dirty with time because of humidity or particles inside the engine that might get into the AC system. However, when you clean it properly, changing your air conditioning filter once per year should be enough to keep it in good shape

What problems does the car AC evaporator coil have?

The evaporator coil is responsible for turning refrigerant into a gas. It uses the low temperature inside the car to make this conversion, which is then sent to the condenser, which in turn pushes it out to the outside.

This part of your AC can get dirty after time because of particles that might get into your engine and will be pushed out through the evaporator. It is easily cleaned and maintained by you without paying for any repair shop

AC filter problems

Also, the car AC air filter itself should be replaced because it can get dirty or clogged over time due to humidity or dirt particles inside your car. Changing this filter once per year is highly recommended.

How to eliminate the strange noise in the car AC system?

In most cases, even if you have determined exactly where the unpleasant noise comes from, and guess what caused it, self-repair of the car air conditioning system is not recommended. 

The rumble, noise, hum, or whistle when the climate system is turned on indicates that the compressor can no longer work in normal mode. 

Sometimes, a quick fix is adding a little oil to the compressor. This is exactly what many car owners do. But, by doing so, they only postpone the failure of this most important part of car AC. A better way of dealing with this issue is to repair it, but even better is to replace it with a new one. This can be costly, but it’s effective.

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