Car Shakes When Heat is On

Car Shakes When Heat is On? Here’s What You Need to Know

Car shaking when AC is on can be incredibly frustrating. Not only that, but it is also a sign of a deeper issue with your vehicle. 

So, what causes car shakes when heat is on? A defective AC system and compressor can cause this issue. Other causes include weak engine mounting, loose hoses, an overloaded engine, and malfunctioning engine sparks. A defective fuel injector and throttle body can also lead to the issue.

This article will take you through the causes and solutions for a car shaking when the heat is on. Don’t let the shaking ruin your driving experience any longer; get the answers you need by reading on.

What Causes a Car Shake When Heat is On?

What Causes a Car Shake When Heat is On

Here are the things that cause car shakes when you turn your AC on.

1. Defective AC Compressor

The AC compressor is a vital component of the air conditioning system and compresses and circulates refrigerant throughout the system. 

When the compressor is damaged or worn out, it can cause poor cooling performance and strange noises from the AC compressor. Additionally, the compressor may struggle to maintain the correct pressure, causing vibrations or shaking as the system overworks.

Defective AC Compressor

2. Load on the Engine

When the engine is under a huge load, it can cause vibrations or shake. This is because the engine works harder to maintain its speed or accelerate. And it can happen when climbing a hill, towing a heavy load, or driving on a steep incline when you turn the heater on. 

What Causes a Car Shake When Heat is On

The increased load on the engine can cause the engine to misfire or cause the pistons to work harder than usual. This can result in vibrations or shaking that can be felt throughout the car.

3. Defective Fuel Injector

The fuel injector is responsible for delivering fuel to the engine in the correct amount at the correct time. It can cause poor fuel efficiency, engine misfires, or stalling when it malfunctions. Additionally, the engine may not receive the correct fuel, causing it to run rough and vibrate excessively.

Defective Fuel Injector

4. Malfunctioning Spark Plugs

Spark plugs are responsible for igniting the fuel in the engine; if worn out or obsolete, they may not be able to ignite the fuel properly. As the spark plugs deteriorate, the engine may struggle to run. When you add the heater load, it will surely vibrate.

5. Failed Engine Mounting

Engine mounting is responsible for keeping the engine securely in place. If the engine mounting fails, it can cause vibrations or shaking when the engine is running. The vibrations will become more pronounced when you turn your AC heater on as the engine has to work harder to generate heat. 

Failed Engine Mounting

6. Loose Hoses

Hoses carry fluids throughout the engine, such as coolant, oil, and power steering fluid. When the hoses are loose, they may not be able to properly carry the fluids, leading to poor engine performance, coolant leaks, or overheating. 

When you turn your heater on, your engine works extra hard, leading to vibrations as it does not have enough essentials to run. This loose hoses’ movement can also cause vibrations or shaking.

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7. Contaminated Throttle Body

The throttle body controls the air flowing into the engine. When the throttle body is contaminated, it may not be able to control the airflow properly. And that leads to poor engine performance, rough idle, or stalling. 

So, when you turn your heater on, the vibration will become more noticeable. Additionally, the throttle body may stick or not open or close properly, causing the engine to run roughly when you have the AC on.

Contaminated Throttle Body

8. Weak Alternator

The alternator generates electrical power to charge the battery and power the car’s electrical system. When the alternator is weak or failing, it may not generate enough power to charge the battery or power the electrical system. 

This can lead to the electrical system not functioning correctly, such as the heater. And the lack of power can cause the heater to struggle to function, leading to vibrations or shaking. 

Moreover, the alternator may not be able to maintain the electrical system’s voltage. Thus, this can cause the electrical system to malfunction, resulting in vibrations or shaking.

Step-by-step Guide on how to Fix Car Shakes When Heat is On

how to Fix Car Shakes When Heat is On

Follow the steps below to diagnose and fix the issue:

1. Perform a Visual Inspection of the Vehicle

During this step, you will be looking for any obvious signs of wear or damage on various components of the vehicle that could be causing the problem.

how to Fix Car Shakes When Heat is On

Step 1. Look for any loose or damaged hoses or wires. 

Step 2. Inspect the engine and transmission mounts for any signs of wear or damage. Check for any leaks or cracks which could be causing the problem.

Step 3. Inspect the AC compressor for any signs of damage or leaks. The AC compressor is located in the engine bay.

2. Check the Engine Performance

The next step is to check the engine performance. This can help determine if the problem is related to the engine or the transmission.

Check the Engine Performance

Step 1. Confirm the engine oil level and condition. Check the oil for any signs of contamination, which can cause the engine to overheat.

Step 2. Check the coolant level and condition. A low coolant level can cause the engine to overheat, which can cause the car to shake when it is overloaded.

Step 3. Be vigilant for any warning lights or error codes. Warning lights or error codes can indicate a problem with the engine or transmission, which can cause vibrations or shake.

3. Inspect the Electrical System

The next step is to check the electrical system, which can help determine if the problem is related to the electrical system or the battery.

Step 1. Look for corrosion or damage. Corroded or damaged battery terminals can cause the electrical system to malfunction, leading to vibrations. 

Step 2. Check the alternator for any signs of wear or damage. Inspect the alternator belt for wear or damage and ensure it is tightly tensioned.

Step 3. Ensure AC wiring isn’t damaged. Look for any frayed wires, loose connections, or corroded terminals.

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4. Check the Heating System

This step can help determine if the problem is related to the heating system. Inspect the heater hoses for any signs of wear or damage. Leaks or damage to the heater hoses can cause the coolant to leak. This can cause the heater core to malfunction and cause vibrations or shaking.

Check the Heating System

5. Take the Car for a Test Drive

After the inspection, take the car for a test drive and pay attention to any vibrations or shaking. Check the engine performance, electrical system, and heating system while driving. This will help you to identify the problem more clearly and to confirm the diagnosis made in the previous steps.

6. Fix the Issue

Based on the diagnosis and inspection, fix the issue by replacing worn or damaged components. Replace the spark plugs, fuel injectors, hoses, and belts if needed. 

Replace any worn-out or damaged engine mounts. Replace the AC compressor if it is defective. Install a new alternator if it is weak.

Fix the Issue Car Shakes When Heat is On
If your car shakes when the heat is on, you might find our articles on car shakes when parked and car shaking after oil change helpful. Our article on car shakes when parked discusses how suspension issues, tire problems, or engine mount issues can cause shaking while the car is stationary. Meanwhile, our article on car shaking after oil change explores some of the common reasons why this issue can occur, such as overfilled or low engine oil levels, a clogged oil filter, or using the wrong oil viscosity. Be sure to check out our resources on car shakes when parked and car shaking after oil change for more information.

FAQs

Here are answers to common questions that might come up when troubleshooting the problem:

Q: Is it Normal for the Car to Shake a Little When the Heat is Turned On?

No. It is not normal for a car to shake when the heat is turned on. While a small amount of vibration may be expected for some cars, excessive shaking or vibrations can signal a problem with the heating system or other components.

Q: Can a Worn-out Suspension System Cause Car Shakes When the Heat is On?

A worn-out suspension system can cause car shakes or vibrations, but it would not be specific to when the heat is turned on. It can cause the car to shake or vibrate even when the heat is not on, such as when driving on rough roads or during turns. 

Conclusion

If you are experiencing car shakes when heat is on, it could mean many things, as discussed above. It is up to you to narrow down to the specific cause and rectify it to do away with the vibrations. However, regular maintenance is critical to prevent this from happening in the future. 

Ensure you do regular check-ups on your vehicle, check the fluid levels, and inspect the hoses, wiring, and belts. Also, pay attention to any warning lights or error codes on the dashboard to identify problems in advance.

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