Car Shakes When AC Is On (Explained)
Does your car shake when you turn on the AC? If yes, this is a warning sign that your car has a problem that needs to be fixed. But first, you need to know what causes your vehicle to tremble when the Ac is on.
Car shakes when AC is one mainly due to a bad AC compressor or broken/worn motor mounts. The shaking problem could also be caused by bad spark plugs, faulty fuel injector, load on the engine, dirty throttle body, and bad throttle position sensor.
In our guide below, we’ll dig deeper into all the most likely causes for your car to shake when AC is on. We’ll also discuss how to fix the problem before it leads to more damage to your car components.
Why your car shakes when AC is on?
When you turn on your car’s air conditioning, it ought to run smoothly and make you feel cool and comfortable. However, sometimes it can end up being a nuisance by making your car shake and making you feel uncomfortable.
That said, knowing what causes the shaking when your car AC is one is the first step to solving this problem.
Here are the most common reasons why your car shakes when AC is on:
- Faulty AC compressor
- Damaged or worn motor mounts
- Bad spark plugs
- Faulty fuel injector
- Too much engine load
- Bad throttle position sensor
- Dirty throttle body
Let’s have a closer at how each of these factors makes your engine shake when you turn on your car air conditioning…
Bad AC compressor
If your car is shaking violently, a faulty AC compressor is one of the most likely causes. When this part goes bad, it adds pressure to your car engine when you turn on the AC.
The compressor simply cools off the AC refrigerant before it is sent to the condenser. Thus, if the compressor fails, it will put a strain on your car engine, making your car shake when stopped and the AC is turned on.
A defective compressor will also send high amounts of debris to your AC system, risking severe damage to various parts of your car.
You can tell if your AC compressor is faulty by accelerating your car with the AC on and off. If the shaking increases when the AC is on, chances are high that you have a faulty compressor.
However, this isn’t a foolproof method for diagnosing the compressor issues, and you should still get a professional to check your compressor for any issues before you set to replace it with a new one.
Damaged or worn motor mounts
Your car shaking or rumbling when the AC is on could also be a sign that the motor mounts are worn. These mounts are essentially designed to help isolate your engine vibrations from the rest of your car structure so you can’t feel them.
When you turn the AC on, it loads up the engine more, resulting in increased vibration. Because worn-out motors can’t dampen the engine vibrations, you’ll start feeling your car starting to shake which can be quite annoying.
All you need to do in this case is replace the damaged motor mounts with new ones which will dampen and isolate the engine vibrations from the rest of your car.
We recommend having a mechanic do the replacement for you. This is not a DIY job as most folks believe since you’ll need to jack up your car motor to replace the damaged mounts.
Too much engine load
Did you know that your Ac unit puts a lot of strain on your engine? This additional stress on the engine will make parts of your engine wear out.
And your car is likely to shake or vibrate when you turn on the AC. The more damage the strain causes, the more violent the shaking becomes.
Bad spark plugs
Damaged or worn-out spark plugs can also make your car shake when you turn on the Air conditioner.
The plug is tasked with producing the electricity needed by the engine to blend air and fuel.
If the spark plug is unable to do its job, the engine will not get the speed and power it requires during the initial power production.
This makes your car shake when the air conditioning is turned on. Replacing all your spark plugs with new ones will help fix this issue.
Faulty fuel injector
A bad fuel injector can also cause your car to start shaking when you turn on the AC. The work of this component is spraying and controlling fuel flow.
It works with electronically controlled valve to open/close as many times every second.
When the injector goes bad, it will strain your engine and this will result in your car shaking when you put on the AC.
Bad throttle position sensor
The work of throttle position sensor (TPS) is to control your engine air intake. In other words, it controls how far the throttle valve opens.
And this is usually determined by how far you’ve pushed the gas pedal.
That said, if the sensor becomes faulty, it cannot control your car’s RPM. Therefore, when you turn on the AC, the RPMs will be inconsistent and your car is going to shake.
Dirty throttle body
The throttle body helps maintain air-flowing system in the car engine.
Since this component involves air passing in its operation, it can get dirty quickly and make your engine unable to get enough airflow.
The result is that your car will start vibrating when you turn on the AC as it is unable to maintain proper airflow.
How do you fix car shakes when AC is on?
The best way to fix your car shaking when AC is on is to first find the source of the shaking. There are many possible causes as you’ve seen above, so a diagnosis will be needed to find what’s causing the vibration.
If you have tried operating your car with the air conditioning off and it doesn’t shake, then that’s a confirmation that the AC is the source of the shaking.
We advise you to have a professional auto mechanic check your car. A trained technician will be able to do a more effective diagnosis and easily find out what’s mailing your engine. A good place to start is your local mechanic or AC repair services.
What causes rough idle when AC is on?
Sometimes your car may shake when idle, say at a stop light, with the AC on and it stops when you switch off the AC. This is the case of this redditor whose brand new Subaru experienced some mild shake at idle.
If this happens to you, it could be a case of the air conditioning unit straining your engine. As your Ac is running, it slightly draws down the idle.
When you combine the low idle with some bit of load resulting from turning the compressor, your engine is likely to vibrate.
If the shaking is more intense and you can even feel it in your steering wheel, then it could be a sign that the motor mounts are going bad.
Dirty or damaged idle air control and dirty throttle body are unable to do a good job and this may be another reason your car shakes or rumbles when the AC is on. Having these components can help resolve the issue.
All in all, it’s best to have your car checked to determine what’s causing the shaking. The earlier you have a mechanic check your car, the faster you’ll have the problem solved and take your car back to idle.
What if my car shakes more when ac is on?
Your car may already have a shaking issue which intensifies when you turn on the air conditioner. In this case, there are a number of possible reasons behind the shaking.
For instance, the AC compressor could be putting a lot of stress on the engine, making the shaking worse.
When you turn on your air conditioning, the engine control unit triggers additional components to activate including idle air and speed control motor.
This helps slightly increase idle and compensate for the compressor’s extra drag.
If this doesn’t happen, the extra drag may result in a low and shaky idle—end even making the engine stall.
Shaking that amplifies with the Ac turned on could also be a sign of weak or damaged motor mounts. broken mounts lose their ability to dampen/isolate your engine vibrations, so you can easily feel them.
Add this to the engine stress caused by the engine and the vibrations will only get stronger.
We advise you to get a mechanic to diagnose your engine shake problem and found out the exact cause so you can fix it.
What does it mean if the brake pedal vibrates when AC is on?
You may also have a case where your brake pedal vibrates when you turn on the AC.
This redditor explains clearly how this feels like; he heels the vibrations through his brake pedal when parked or stopped at a red light with the AC on.
So, what’s the likely culprit behind this issue? Most experts suggest that this issue usually happens due to your car RPMs dropping whenever the air conditioning engages.
You can try turning off your air conditioning and then raising the RPM up 200-300 to see if it helps solve the issue.
You may also want to ascertain if the vibration has anything to do with your AC in the first place. Just turn off your AC and see if the brake pedal continues to vibrate.
If it doesn’t, you may want to look at other likely culprits for your pedal vibrating.
These include improper wheel alignment, issues with the rotors, failing brake pads, or worn-out braking system parts.
If your car shakes when the AC is on, it could be a sign of a problem with the engine, AC compressor, or AC system. However, this issue could also be associated with other common problems, such as car shakes when driving slow or when stopped. To learn more about these potential causes and what you can do to fix them, check out our articles on car shakes when driving slow and car shakes when stopped. These articles provide helpful tips and insights on how to troubleshoot and solve these issues, so you can ensure the comfort and reliability of your vehicle and prevent any potential damages.Related Questions:
You can fix rough idle when AC is on in your car by first finding what’s behind the shaking. The most common cause is a dirty throttle body which you can simply clean and unblock to solve the issue. Other likely causes include damaged engine mounts, defective cooling fan, and worn-out spark plugs which require replacement.
The most common causes for sputtering in your car when air conditioning is on include faulty idle air control valve, malfunctioning condenser or cooling fan, dirty throttle body, or issues with spark plugs.
A failing AC compressor can cause a sudden increase in carbon buildup, resulting in rough idle when your air conditioning is running.
Final Verdict
Car shaking when AC is on is one of the most common problems experienced by car owners all over. The most likely causes for this problem include bad motor mounts, a failing AC compressor, and the extra stress put on the engine by the AC. Faulty fuel injectors, dirty throttle body, and/or throttle body sensor are also potential culprits.
The best way to fix this issue is to first find out the culprit behind it. That’s why we advise you to have an experienced mechanic diagnose your car to find out the root cause and resolve it. Most of these issues are simple and cheap fixes. However, some parts may require replacement but they’re still within affordable range.
