Car Shakes When AC Is On: Causes and How to Fix It

When your car shakes when AC is on, it is a sign of a problem that needs to be dealt with. Most people think that this happens only when there is an issue with the AC compressor. However, it could be a result of various things that we shall discuss in this article. To get a good understand of this, it is essential to know the engine part’s names and how they function with the AC compressor. 

The AC compressor is an integral part of the vehicle. It cools the interior air of a car in hot weather, thus providing a conducive environment for the occupants. With this understanding, it will be easy for you to know when the AC systems fail and how to prevent them. In this article, we shall learn why the car shakes when AC is on and how to fix the issue.  

What Causes Car Shakes When AC Is On?

Air conditioning is a common feature in all new vehicles. The AC has two functions. One is to raise the refrigerant pressure. The refrigerant must be hotter than the ambient temperature for heat transfer to take place. 

The second function is to create low pressure in the evaporator. This enables the refrigerant to vaporize, thus enabling it to absorb heat energy from the vehicle’s cab. It also circulates the compressor oil and refrigerant, which mix throughout the AC system. Here are the reasons that make your car shake when the AC is on:

Car Shakes When AC Is On

Load on Engine

The AC acts as a small engine, and it puts too much stress on the engine. When you turn the AC on, the vehicle engine triggers elements such as idle speed or air control motor. You can increase the idle compressor by compensating with an additional drag. The inaccuracy in this process causes the vehicle to shake when AC is on. 

In most cases, the additional drag can lead to the steering wheel vibrates when ac is on. When you turn the steering wheel with the AC is on the chances of engine stalling increase. If the AC continues loading the engine, some engine parts will wear out, eventually needing replacements. 

Engine Foundation/ Mounting

The engine mountings hold the suspension and engine into place. The mounts hold the engine and transmission at the right suspension angle. When you turn the Ac, the mounts go through a lot of strain. Therefore, when the engine mounts or foundations wear out, you will experience vibrations and shakes when the AC is on. 

If the engine mount is broken, the vibrations will increase, and noises will accompany them. Therefore, when you start experiencing the vibrations, call your mechanic to check if the mounts are in order or need to be replaced. 

Bad Throttle Position Sensor

Another reason why car shakes when starting is due to a malfunctioning TP sensor. A faulty TP sensor does not control the RPMs. Therefore, when you turn the AC and the RPMs are inconsistent, the car will shake. To solve this issue, you need to clean the sensor or have it replaced. 

Faulty Fuel Injector

The fuel injector pumps sufficient fuel into the engine at the right time. If the fuel injector is malfunctioning, the engine will not get enough fuel, reducing its effectiveness. When the AC is on, it strains the engine further, and the vehicle starts vibrating. If this is the cause of the vibrations, then the fuel injectors will need to be replaced.  

Damaged or Old Spark Plugs

A damaged or old spark plug is the other reason why your Honda Accord shakes when the ac is on. This is caused by a lack of connection during the initial power generation. This could even be as a result of one worn-out or broken spark plug. In this case, the plugs in question need a replacement immediately before they lead to further damage. 

Damaged AC Compressor

Another main reason that could cause car shakes when accelerating is when the AC compressor is faulty. A damaged AC puts an excess load on the engine, thus resulting in massive vibrations. To diagnose this, accelerate the vehicle when the AC is on. If you note a difference in the pick, you need to replace the AC. 

How to Fix Car Shakes When AC Is On

As we have seen above, various factors can cause the car to shake when the AC is on. Therefore, the way to fix the issue will depend on what causes the shaking. The most common cause of AC that makes cars idle rough is a dirty throttle body. In this case, follow these steps:

  • Open the vehicle hood
  • Check the throttle body carefully
  • Ask a partner to turn the car key to the “ON” position. They should not start the engine.
  • Ask the perform assisting to press the accelerator slowly
  • Spray a throttle body cleaner on a clean cloth
  • Use the cloth to clean the throttle body carefully

If a dirty throttle body was the cause, then you will have fixed the issue. In some cases, this problem would be due to a faulty AC compressor. In this case, you will be required to change and replace the AC compressor.

Engine shakes when a/c turns on a simple fix YouTube

Frequently Asked Questions (FAQs)

Q: What Causes Rough Idle When AC Is On?

There are various reasons why the vehicle could rough idle when the AC is on. The leading causes of rough idling are a dirty or faulty AIC valve, faulty condenser or cooling fan, dirty throttle body, damaged or old spark plugs, and worn-out engine mountings. Some will need you to just clean to solve these problems, and others require you to replace the parts entirely.

Q: How Do You Fix a Rough Idle When AC Is On?

Fixing a rough idle when AC is on will depend on the cause. The most common cause is a dirty throttle body. In this case, you can solve the issue by cleaning and unclogging the throttle body. If old and worn-out spark plugs cause it, the solution will be replacing them with new ones.

At times the AC itself could be faulty, and it needs replacement. Therefore, it is advisable to visit a professional mechanic who will help find out what the actual cause is, and then you will get to know how to fix it.

Q: Will a Bad AC Compressor Affect the Engine?

A bad AC compressor does affect the engine. The AC compressor is a significant part of the air conditioning system and derives its power from the engine. The AC compressor pressurizes the AC system and keeps the refrigerant flowing for the system to work perfectly.

A malfunctioning AC compressor makes the vehicle shake when the AC is on, and in extreme cases, it can make the engine stall. AC compressor shaking is a major sign that tells you that the system at the verge of failing.

Q: How Can I Make My Car Idle Smoother?

The smooth idle of a vehicle depends on the right mixture of air and fuel. Therefore, if the air and fuel are not processed properly, you will have a rough idle. There are various causes of rough idling. To get a smooth rough idle, you need to know the exact cause of its rough idling.

In most cases, it is due to components that control ignition and fuel. Therefore, the prudent thing is to check these components one by one. If they are clogged, take some time to clean them. If the parts are worn out, the way to a smooth idle is by replacing them.

Final Words

Car shaking when AC is on is one dilemma that most drivers find themselves in. the above information will help you know when the problem occurs, why it happens, and how to fix it. Some people make the mistake of waiting, hoping that the issue will disappear.

Car shakes when ac is off could be caused by different factors. The prudent thing to do is to have it fixed as soon as you discover it to prevent it from worsening. Always make sure that the AC system in your vehicle is working correctly and does not affect the car’s power.

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Hi there, I am R. Hasan Tito, a mechanic, and owner of this website. My friend and I created this website to share our knowledge, expertise, and experience with our fellow mechanics' community and car users. I am a specialist and certified automotive mechanic (Both Heavy Commercial and Private Cars). I worked as a Mechanic and Mechanic Supervisor for over fifteen years at Global Rebound Automotive companies - Toyota, TATA, BMW, Nissan, TVs, and Others. Now, I enjoy my new role of leading a team of automotive experts (in their respective fields) and publish new content on a regular basis on my website and social media.

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