Why Does My Car Overheat When The A/C is On? (Solved)

When the summer heat is above average, all you need is to turn on your AC and enjoy a cool breeze from your car. Unfortunately, this is not always the case.

Sometimes you turn on the A/C, and the car overheats.

If you have found yourself in that situation, you know how frustrating it can be. In this article, we will discuss some of the major reasons why your car will overheat when you turn the AC on. We will also share with you a solution for each case.

Why Does My Car Overheat When The AC Is On?

There could be several reasons why your car overheats when the air conditioning (AC) is on. The AC system may be low on refrigerant, the AC compressor may be faulty, or the radiator may be blocked. It is recommended to have a mechanic diagnose and fix the issue to prevent further damage to your vehicle.

Components in Cooling System of a Car

The cooling system of a car includes multiple components. Here’s how the components make the cooling system work. 

Cooling Fan

The role of a cooling fan is to slow down or speed up as per the engine’s temperature. It keeps the engine cool and doesn’t let it overheat quickly. 

Water Pump

Another component is the water pump, the car’s drive unit. The role of a pump is to supply water to the cooling system. It doesn’t impact engine oil. 


Next comes the radiator, which helps remove the waste heat from the engine. 


The last component is a thermostat that works efficiently to maintain the engine temperature. 

What are the Symptoms of a Bad AC Compressor?

Car overheating when the air conditioner is on is a common issue. But how will you know that you have faulty AC? The below-mentioned signs can help you know. 

Car’s Interior Component Feels Hot

If you notice the car’s interior component getting hot, it might be a sign that your car has a bad AC compressor. When the interior component gets hot, a burning smell comes from the car or air conditioner.

Car’s Temperature Gauge 

Another sign indicates an issue with cars overheating when the AC is on. You can read the car’s temperature gauge to know about the overheating condition. 

The car’s temperature gauge tells about the temperature of the engine’s coolant. The average temperature should be somewhere between 195 degrees and 220 degrees. If the car’s temperature gauge reading is more than 220 degrees, that means the vehicle is getting overheated. 

Car Engine Shuts Down

If the car overheats, it would automatically shut down irrespective of the cause. You can try turning on the car’s AC. If the engine suddenly stops, it indicates you have a faulty AC system. 

Cloud of Steam Coming Out From Under of Hood

It’s the traditional way of understanding whether there is a problem with the car’s AC or not. Apparently, the car is overheating if you see a cloud of steam under the hood.

Why does my car overheat when the A/C is on?

1. Worn AC Compressor

Worn AC Compressor

This is one of the major reasons why your AC will overheat. This is especially if the car overheats only when the AC is turned on, and temperatures go down when the AC is turned off.

If this is the problem you are experiencing, then the AC system is faulty, and the AC compressor is the main reason for this change.

The AC compressor connects to the engine through the serpentine belt. When the engine turns on, the belt starts to spin. It delivers a power AC compressor.

An AC compressor with worn-out seized pulley, bent, or bad bearing will put ab extra load to the car engine. This makes it work harder when the AC is turned on.

The overloaded engine starts to overheat. And this is what brings the excess heat you experience in your car when the AC is turned on.

In the case of a damaged AC compressor, the overheating comes from an overloaded car engine.


If you notice this kind of heating, quickly turn off your AC. If you don’t, the engine might start melting and destroying itself from the inside. Turning off the AC will make the car engine operate normally.

If the compressor is the problem, go ahead and buy a new compressor. Replace the defective parts to get the best performance from your car.

The following are the best compressors you will find in the market. But the one that fits over your car AC system.

ACDelco 15-20941 GM Original Equipment Air Conditioning Compressor and Clutch Assembly

  • Perfect for all General Motors Vehicles
  • Original factory component
  • Reliable, durable, and high quality

Click here to check the latest price and buy it from Amazon now.

UAC CO 29002C A/C Compressor

  • OE replacement
  • Add your car model on Amazon to check the fit
  • Perfect performance

Click here to check the latest price and buy it from Amazon today.

2. Dirty Or Old Coolant

Dirty Or Old Coolant

Coolant can last for a long time without the need for replacement, but eventually, you will need to change it. When the coolant becomes old or dirty, it stops cooling your car as a coolant should.

This means your car engine will start to overheat if the coolant is not doing a good job.

The problem becomes worse when the car AC is turned on. The AC requires some extra power from the engine. This means that the engine will produce some more heat.

That’s why you will notice that your car will begin heating when the AC is turned on. Low coolant levels can affect the air conditioning system because the AC relies on the engine’s cooling system to function properly.


The solution to this particular problem is simple. Replace the coolant. Get a coolant that will give you high performance for your car.

This is the only way you will solve this problem.

Another reason you will need to replace the coolant is to protect other car engine components from corrosion and rusting.

BMW 82141467704 Coolant/Antifreeze is the best coolant you will find in the market. If you wish to get, the best cooling effect flushes your current coolant and replace with it. Click here to check the coolant and buy it from Amazon now.

3. Defective Cooling Fans

Cooling Fans

If your car overheats when idling after turning on the AC, the fans could be the blame.

A car cooling system has a radiator – a system of fins behind the car grille. The role of the radiator is to draw the excess heat away from your car and flows through the fins. This is how it keeps the engine cool.

When the car is idle, the cooling fans should be working to provide enough cool air circulation into the system. So, when the car is idle, and fans aren’t working, you start feeling excess heat.


If this is the case, you might need a new cooling fan, cooling fan motors, or electrical connection for the fans that are affected.

So, when you notice your car overheating when the AC is turned on, and the car is idle, check the fans. This is likely to be the problem you are dealing with.

car overheating
Source: reddit@Puzzleheaded-Big7990

4. Damaged or Blocked Radiator

In the case, your cooling fans are functioning perfectly, but the car still overheats when idle, then the radiator could be the problem.

In most cases, you will find that your radiator is blocked. This happens if your car sucked a cardboard sheet, plastic bag, or other elements that could block the grille, it blocks the airflow. You won’t have enough air flowing through the radiator.

If this happens, the car will overheat even when an AC is turned on.

why does my car overheat when the ac is on


To deal with this problem first check through the grille. See if anything is blocking the air passage.

Sometimes you will find that the radiator is damaged, too old, or dirty. As a result, it doesn’t exchange heat properly.

With time corrosion also build up on the inside fins that slow down coolant flow. As a result, the cooling performance is reduced.

In short, to deal with this problem, you need to check any damages or blockages on the radiator.

Read Also: How to bleed off an overcharged AC: Steps That works

Besides this, a few more reasons result in the car overheating when the air conditioner is on. 

Compressor Overload 

Does your car have a multifunctional compressor? If so, then it might put a lot of pressure on the load on the car engine. The thing is, multifunction needs a large amount of power from the engine. 

The compressor generally cannot handle this pressure. The compressor of the AC can further put a rational load on the engine. As a result, the compressor gets exhausted, which overheats the car engine. 

Inadequate Cooling System

Car overheating when the air conditioner is on can also be caused due to an inadequate cooling system. The main role of a cooling system is to keep the AC condenser cool when the air conditioner is working. 

The usual scenario is when you turn on the AC, the air conditioning cooling system reduces the heat. However, when the cooling system becomes defective, the car overheats. 

A faulty water pump, defective condenser fan, and clogged condenser fan can malfunction the cooling system. 

Faulty in-vehicle Components 

Did you know that faulty in-vehicle components can also make the car overheat when the air conditioner is on? Faulty components like the refrigerator, evaporator, compressor, and condenser can put pressure on the air conditioner. It, in turn, increases the car’s temperature. 

If you want to reduce the possibility of car overheating due to faulty components, you must regularly check the components. If the components are working efficiently, everything is fine. But if you find something even minor, get it resolved; otherwise, it would cause the car to overheat when the AC is running.

Other Solutions for Car Overheat when AC is on

Besides trying the aforementioned solutions, you can also try these solutions to fix the car overheating problem with AC on. 

Flush the Coolant System

When a car overheats, the best thing to do is to flush the coolant system. You can regularly keep an eye on the coolant system to make sure that you do not end up with an overheating car when AC is on. 

Check the Refrigerant 

Undoubtedly, refrigerant is an essential part of the vehicle. Thus, it becomes your responsibility to check for the refrigerant regularly. Regular checking and maintenance will make sure that the car doesn’t overheat with AC on. 

If you think there is an issue with the refrigerant, immediately take your vehicle to a mechanic rather than avoid the issue. 

Check the Condenser

 The condenser present in the air conditioner is actually a radiator positioned between the engine cooling radiator and the car’s grille. After checking the condenser, if you find a problem, you must clean it right away. Bad condensers don’t work properly, which causes the engine to overheat when AC is on. 

Add Water to the Radiator 

Did you know that you can keep the radiator working in good condition by regularly adding water to it? If the radiator is dry, you must add water, so it doesn’t wear off. 

After adding water to the radiator, the car’s water pump takes it and moves through the motor back to the radiator. 

What to do if Car Overheats with AC on in Traffic 

At certain times, the car might overheat with AC on in the traffic. But what to do? 

Being stuck in traffic is irritating, and if the car overheats with AC on, things get even worse. But don’t worry because we know what you can do if a car overheats with AC on in traffic. 

Pull Over Your Vehicle

First thing first, you must pull over your vehicle as soon as you notice a car getting overheated. However, in certain cases and places, pulling over the vehicle is not possible. 

Turn off the Car Air Conditioner 

If you cannot pull over your vehicle, you can immediately turn off the car’s air conditioner. Also, after pulling over your vehicle, you can turn off the AC. It will help the engine to cool a bit. 

Turning off the car air conditioner works best if the car is parked and neutralized in a safer place. 

Open Your Car Hood 

The best thing you can do to cool down the car overheating when the air conditioner is on is to open the hood. But if the hood is also too hot, avoid touching it. Let the good cool down. Then you can open the hood and let the steam go. 

Turn off Engine

Another thing to do to cool down the vehicle in traffic is to turn off the engine. But you must keep the key in the ignition. Doing this will keep the fan running, eventually releasing the heat. 

But if the fan is not working, it’s probably because the main culprit for heating is the fan itself. In this situation, it’s advised to take the vehicle to a mechanic. 

Wait for Approximately 30 Minutes 

The estimated time your vehicle needs to cool down is 30 minutes. Once your car gets cold, you can start the inspection to look for signs of leaks. If you can’t find the issue, consult a professional mechanic to resolve the issue before it grows bigger. 

Frequently Asked Questions 

Can running AC cause cars to overheat?

Running the AC puts extra load on the engine, which can contribute to overheating in vehicles with a compromised cooling system. However, a properly functioning cooling system should handle the extra load without issues.

Can a bad AC compressor cause a car to overheat?

A faulty AC compressor can cause a car to overheat if it seizes and causes the engine to work harder or if the serpentine belt gets stuck, increasing the load on the engine.

Can the AC cause the car to overheat?

The short answer is yes. In most cases, it happens because the AC compressor gets power from the engine shaft. It puts pressure on the engine. Remember that if more power is generated in the engine, it will result in wasting more heat. 
Since the cooling component does not remain powerful enough to remove the excessive heat, the car overheats. 

Why does the temperature gauge go up when AC is on?

You might know that the engine also gets overheated when the AC comes on. But there is more to notice than just the temperature gauge going up. That’s because, at certain times, the temperature gauge even goes up due to the coolant temperature sensor malfunctioning. 

Why does the car overheat when idling with AC on?

The car overheats with the air conditioner on not only when it’s running but also when idling. It usually happens due to faulty fans. When the fan gets defective, it no longer enhances the heat transfer between hot coolant and outside air. 
So, when the fan gets faulty when idling, the air does not blow past the radiator and condenser fins. Thus, the car overheats. 

Can I drive my car with a bad AC compressor?

You can drive the car with a faulty AC compressor as long as you don’t need cool air blowing inside the car. But it’s advised to fix the issue quickly instead of overlooking it.

Parting Shot

If your car overheats when the AC is turned on, chances are there is a problem with the car cooling system or engine.

Check for signs of any of the four problems we have shared with you in this article. Fix them. But if nothing seems to change, seek professional help. Get help from a qualified mechanic. 

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