Car Diagnostic

5 Reseasons Why Car Shakes When AC Is On

Mike Cross
Updated Nov 15, 2021
Car Shakes When AC Is On

Cars are delicate machines and see a great deal of maintenance during general use. The average vehicle lasts for about ten years, but plenty of issues can change that. One common issue is suffering from car shakes when the AC is on.

If you’ve been suffering from a similar issue, we’re here to help. Read on for some of the most common causes as to why your car vibrates when the AC is on.

1. Strained Engine

One of the most likely causes is that the air conditioning is causing some sort of strain on your engine. This increased strain on the engine could cause parts of the engine to wear out. In turn, this leads to the vibration or shaking of your car when the air conditioning is on.

Most notably, this happens when the AC compressor strains the engine. More severe shaking can mean that the damage is also more severe. When you notice this shaking, bring your car to an air conditioning technician as soon as you can.

If this goes untreated, the strain on the engine will continue to worsen. As the vibration grows more severe, the damage is becoming a bigger issue. This shaking can even lead to complete engine failure of your vehicle if untreated.

2. Loose Mountings or Foundation

A less severe cause could be loose mountings on your engine or the foundation. While this is “less severe” in terms of the damage it causes to your engine, loose mountings can lead to other issues. An insecurely installed engine could cause intense damage or an engine failure, especially while driving.

While this isn’t a direct cause of your air conditioning, this can be caused by increased stain. Regardless of your AC, you need to fix it.

A simple investigation can help decide if there are any issues. It’s best to bring it to a mechanic to check your engine’s mountings. This can require jacking up the car or possibly removing parts. What exact tasks this entails ultimately depends on the make and model of the vehicle.

A skilled mechanic can let you know if loose mountings or foundations are causing the shaking. They can also inform you of any other issue that might cause the shaking. Most times when these issues arise, you’ll need to take it to a mechanic regardless, so it’s a good first solution to find the problem.

3. Faulty AC Compressor

One issue that doesn’t have to do with the engine directly is your air conditioning compressor. A faulty AC compressor can cause your entire vehicle to shake violently.

Like with loose mountings, the best way to detect this issue is to simply look. A good trick is to accelerate your vehicle with the air conditioning on or off. If the shaking is significantly worse with the AC on, there is a high chance you have a faulty AC compressor.

Of course, this isn’t a fool-proof way to diagnose the problem. Even if this test seems to hint at the issue being your air conditioning, you should still have a professional check it out. That way you know for certain, instead of spending time and money replacing your compressor and finding out it wasn’t the issue.

4. Failing AC System

While a compressor is a likely cause, it’s far from the only component of your air conditioning system. These systems are complex and can have any number of things go wrong with them. Many of these malfunctions can cause vibration and shaking in your car.

For example, clogged or leaking hoses can struggle to properly get air and coolant through the system. This can cause them to shake, with the vibration directly affecting your car.

A good way to fix this is to work proactively. Having your car undergo regular maintenance can help to fend off issues with a failing air conditioning system. This is more important in climates where the AC is running constantly or in older cars.

5. Malfunctioning Throttle Position Sensor

One specific component of your air conditioning system that can undoubtedly cause shaking is your throttle position sensor. This is one of the pieces responsible for regulating the RPM of your air conditioning. 

If this piece is faulty or malfunctioning, the RPM of your AC is going to vary wildly. This can cause your car to shake with a constantly-changing RPM. 

The best way to fix this is to clean or replace your throttle positioning sensor. Checking this piece is also an important part of the regular tune-up for your car. If this piece is functioning perfectly, your issue is likely somewhere else.

Possible Fixes

Car Shakes When AC Is On
Car Shakes When AC Is On

Your fixes will depend entirely on what your individual problem is, but there are easy ways to diagnose each. The vibration is an obvious symptom and one you can often find the source of with trial and error. If your car doesn’t shake with the air conditioning off, for example, there’s a very high chance your AC is the issue.

The best way to fix or diagnose any problem is to bring your vehicle in to a trained professional. Air conditioning repair services or a local mechanic is the best place to start. By letting experts handle it, the diagnosis is likely more certain and the fix more effective.

If you’re hands-on and know what you’re doing, do your best to work safely and have a backup plan. You always run the risk of not having the proper tools or enough hands to do the work well. Have a mechanic in mind in case you need to bring your vehicle in, and do your best not to drive a vehicle that’s shaking violently for safety reasons.

Driving In

If you’ve been asking yourself, why does my car shake when the AC is on? you need to fix the issue as soon as possible. The vibration poses a threat to your safety while driving and can lead to worse issues. If you have further questions, comments, or concerns, feel free to contact us for more information.

Mike Cross
Life is too short to drive with stock audio

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