Why is My Car AC Making A Hissing Noise: Self-Detect 6 Air Conditioner Noises, Causes & Fixing

Car AC Noise

In general, the car cooling system is relatively silent and should not make strange and weird sounds. The unusual car cooling system sound shows underlying problems. It must be addressed otherwise ignoring signs can worsen the situation and even stop the AC from working in the middle of the highway.

In this powerful article, you are going to self-find the five kinds of car cooling system sounds such as hissing, squealing, clicking, rattling, and buzzing sounds, and their causes and fixes. 

Related Post: Car AC Smells Bad When First Turned ON

Car AC Making Noises & Diagnosing 

The sound generated by the cooling system of a car is an indication of its mechanical conditions. More specifically, it is an auditory representation of the condition of the various components that comprise the cooling system.

The sounds produced typically range from squeaks and rattles to rumbles and vibratory hums – all of which are indicative of a malfunctioning or failing component within the system. A vehicle cooling system produces many types of noises especially while accelerating. Below are the five kinds of car cooling system sounds.

  1. Whistling or Hissing Noise
  2. Squealing Noise
  3. Clicking Noise
  4. Grinding Noise
  5. Rattling Noise Or Knocking Noise
  6. Buzzing Noise

1. Car AC Making Hissing Noise & Fixing

AC System
A/C System

Air conditioner hissing noise is also known as whistling noise, is a type of vehicle cooling system sound. It is produced when you turn OFF your A/C. It is something like a whistling sound. But, be calm, don’t worry it’s not an issue. It is the car’s way of equalizing pressure between the high pressure and low-pressure lines of the air conditioner.

Whenever you turn OFF your Air Conditioner, the refrigerant moves from the high-pressure side to the low-pressure side of the cooling system, as a result, a hissing voice is heard.

If your AC is making a hissing sound coming from the compressor, it could be a sign of a problem. Here are five common causes and how to fix them:

  • Refrigerant Leak: If the refrigerant used in the air conditioner is low, it can make a hissing noise. A technician can use a leak detector to locate and repair the leak. Adding more freon to the system without fixing the leak will only be a temporary fix.
  • Internal Valve Malfunction: If the internal valve in the compressor is not functioning correctly, it can cause a hissing sound. It’s time to replace the valve to fix the issue.
  • Dirty Air Filter: A clogged air filter can cause the AC system to work harder, leading to a hissing noise. Check to see if the air filter needs to be replaced.
  • Condenser Or Compressor Problems: Damage to your AC condenser or compressor can cause car AC hissing noise. Take your car to a mechanic to diagnose the issue and fix it.
  • High Pressure Inside The AC System: When the pressure inside the AC system is too high, it can cause a hissing noise. A technician can check the refrigerant lines and adjust the pressure to fix the problem.

Related Post: How Car Air Conditioner Works

2. Squealing or Screeching Noise When AC Is Turned ON

Worn Belt
Worn Belt

The vehicle cooling system’s squealing sound is a loud screeching type of noise. It is the most common air conditioner problem. The vehicle cooling system squealing usually happens at the start when you run the ac. If the sound coming is loud squealing it is a symptom that your drive belt is loose or expired.

A drive belt, also called a serpentine belt, connects the compressor with the engine. The drive belt turns the compressor, which pressurizes the refrigerant inside the compressor to make cold air. A loose drive belt will not turn the compressor properly and will slip on the compressor pulley, causing a loud squealing sound.

Examine the drive belt with your hands by pushing or pulling it to check its looseness. Similarly, with continuous usage for a long time, the drive belt is subjected to wear and tear, which causes cracks or tears in the belt that gets the belt to slip, and a loud squealing sound is produced. So, replacing the compressor drive belt is a better solution.

Related Post: 7 Basic Parts of Car AC System (With Pics) & Their Functions

3. Clicking Noise Under Hood When AC Is ON Due To Compressor Clutch

Compressor Clutch, Pulley And Coil
Compressor Clutch, Pulley, And Coil

When you turn ON the AC in your car, you hear a low-volume clicking voice, which is normal, because the compressor clutch engages with the pulley, causing a clicking voice. But, if you hear a consistent knocking or clicking noise, then this is a sign that there is a problem.

An AC clicking noise coming from your car’s ac can be caused by many factors inside your car, such as a seized compressor, a jammed pulley, and a low refrigerant. These factors could turn on the air conditioner compressor, then off, then on, then again off causing a repeated cycle of an on and off, which is heard as a clicking voice.

Related Post: How To Fix Car AC Compressor Clutch Not Engaging

4. Car AC Grinding Noise

A grinding sound in an automobile’s cooling system is a rough, metallic sound that is produced when two metal components rub against each other, causing friction. This sound is usually caused by a problem with the AC’s components such as a damaged bearing or a malfunctioning belt and indicates that the system is in need of maintenance or repair. The grinding sound in ac may get louder over time as the problem progresses.

To find the issue of a grinding sound in the vehicle cooling system by inspecting components and checking for damage. If it’s a pulley issue, replace damaged belts or pulleys. If it’s a compressor issue, take the car to a mechanic for repair. Address promptly to avoid further damage.

5. Car AC Compressor Rattling Noise Or Knocking Noise

Compressor Loose Mounting Bolts
Compressor Loose Mounting Bolts

If you hear a rattling noise it is the result of a loose part or faulty component. Whenever the Air Conditioner is started, loose parts (which are not tight enough) or broken car ac components especially mounting bolts of air conditioner components will shake, and make a knocking sound.

A rattling or knocking sound may also be a symptom of a faulty compressor. AC increases the load on the engine and also causes a rattling sound. Some of the factors of rattling sound are a badly worn clutch, stuck compressor pulley bearing, and damaged idler pulley.

A good way to figure out the loose part is to turn ON the A/C and stand back, inspect all parts, and tighten the suspected loose part.

Related Post: 11 Reasons Your Car Air Conditioner Blows Cold Then Warm

6. Car AC Buzzing Noise

If the air conditioner makes noises like a buzzing sound it is a sign of overcharged refrigerant in the vehicle cooling system. When the AC refrigerant is overfilled, it produces the same sound when you turn ON the AC. It happens mostly after servicing the air conditioning system.

Too much refrigerant may lead to component damage and also less cool air. So, it is better to move the car to a professional to take out the extra refrigerant from the AC system.

Related Post: 7 Reasons Your Car Stalls/Shuts Off When AC Is Turned ON

How Much Does it Cost to Fix Hissing Sound in Car AC

The cost to fix the hissing noise in car AC can vary depending on the cause of the issue. If the problem is due to a simple fix like a dirty air filter or a loose hose, the cost could be relatively low, ranging from $50 to $200.

However, if the issue is caused by a refrigerant leak or a malfunctioning AC compressor, the cost can be more expensive, ranging from $500 to $2000 or more. In some cases, the entire AC system may need to be replaced, which can be even more costly.

It’s essential to take your car to a qualified technician to diagnose the issue and provide an accurate estimate for the repair costs. Ignoring a hissing noise from car AC can lead to further damage and more expensive repairs, so it’s best to address the issue as soon as possible.

Expert Tips for Reducing Car Air Conditioner Noise

Here are some tips to reduce sound from your vehicle cooling system:

  • Check For Loose Parts: If the car ac is making noise, check if any parts are loose and tighten them if necessary. Because if ac is running under such conditions it can cause serious damage to your compressor or other parts.
  • Clean The Air Conditioning Unit: Dirt effect the performance so take measures to clean the compressor intake port. Dirt and debris can cause loud noises and reduce efficiency, so cleaning the entire air AC unit periodically can help.
  • Replace Your AC Cabin Air Filter: A dirty cabin air filter can block air flow, causing the AC to work harder and generate more unusual noises.
  • Lubricate Moving Parts: Over time, AC components can become dry and make noisy car ac. Lubricating these parts can help reduce sound levels.
  • Insulate AC Ducts: If your car has exposed AC ducts, insulation can help reduce sound.
  • Choose Quiet Tires: Some types of tires are noisier than others. If you’re in the market for new tires, consider choosing ones that are designed to be quieter.
  • Reduce Vibrations: Vibrations from the engine or other parts of the car can create noise. Installing vibration-dampening materials can help to reduce these vibrations and prevent noise.
  • Proper Installation Of Aftermarket Parts: If you’re installing aftermarket parts like a new stereo system or exhaust, make sure they are installed properly. Poorly installed parts can cause rattling or other noise issues.
  • Use Sound-Deadening Materials: Sound-deadening materials like acoustic foam or insulation can be used to absorb or block out unwanted noise. These materials can be installed on the doors, floor, or roof of your car to reduce road noise or engine noise.
  • Avoid Driving On Rough Roads: Driving on rough roads can create a lot of noise. If possible, avoid roads that are in poor condition or have a lot of bumps and potholes.
  • Have The AC System Professionally Serviced: A professional mechanic can check for any other issues that are making loud sound and make necessary repairs.

Frequently Asked Questions (FAQs)

What does it mean if your automobile’s cooling system produces a loud humming sound?

If your automobile’s cooling system produces such a kind of sound, this noise may be due to an issue with the engine components like the compressor.

What should you do if your car has a loud car and warm air blowing from the air conditioner?

If your car has a loud car and warm air blowing from the air conditioner, it could be a sign that the compressor is having an issue. It’s important to take your car to a mechanic right away to have it checked out.

What could be the cause of a vibration type of sound or sound when turning off your vehicle’s cooling system, and what might need to be done to fix it?

A vibration type of sound or sound when turning off your vehicle’s cooling system could be a sign of a bad compressor, particularly if the sound is coming from very high or low-pressure areas. If left unrepaired, it could lead to the need for compressor replacement.

Is it normal for your vehicle’s cooling system to make a hissing sound?

No, it’s not normal for your car’s air conditioner to make a such kind of sound. The leak could be a sign in the high or low-pressure areas of the system, which can cause damage to the compressor.

What does it mean if there is a constant knocking or clicking voice produced from the side of the compressor when you turn off the AC?

If there is a constant knocking or clicking sound produced from the side of the compressor when you turn off the AC, it could indicate that the air compressor needs to be replaced. It’s important to have a mechanic diagnose the issue, as delaying the repair could end up requiring you to replace the compressor.

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