Car Overheats When AC Is On: Causes, Symptoms, And How To Fix

Suppose your car overheats when AC is on or the temperature gauge goes up when the air conditioner is on. In that case, this situation is going to make car riding much more irritating, especially in summer.

The car’s air conditioning should cool down the car’s interior temperature without making the car overheat.

Although car air conditioning and home air conditioning are both used for the same purposes, but, the car AC works entirely differently.

The car air conditioning system needs a condenser, evaporator, compressor, receiver, expansion tube, and other essential components, and these are connected to the car’s engine.

So, here we are going to know the reasons why a car overheats when AC is on, what are the symptoms of a car overheating when AC is on, and lastly, how to fix the issues of car overheating when AC is on.

What Are The Causes Why A Car Overheats When AC Is On?

what are the causes why a car overheats when ac is on
Reasons Why A Car Overheats When AC Is On

Some of the most common causes for car overheating when ac is on are an overload AC compressor, a faulty coolant temperature sensor, clogged condenser fins, and a failing water pump.

The car engine powers the automobile’s air conditioning system. That’s why you can notice the temperature gauge goes up if there is something wrong with the car’s air conditioning.

Here are some common reasons why your car overheats when ac is on:

  1. Bad Coolant Temperature Sensors
  2. Clogged Or Bad Car Radiator
  3. Water Pump Is Failing
  4. AC Compressor overload
  5. Clogged Condenser Fins
  6. The Cooling Fan Is Not Working
  7. Bad Cooling System

1. Bad Coolant Temperature Sensors

Engine Coolant Sensor
Car engine coolant sensor

Coolant temperature sensors or engine coolant temperature sensors are responsible for measuring the car engine’s temperature.

The car’s computer, known as the engine control module, communicates with coolant temperature sensors to run the engine at optimal temperature.

But, bad coolant temperature sensors provide wrong temperature reports to ECM.

When the engine control module gets the wrong measurement of temperature, the ECM gives the wrong direction to the car’s cooling system, and eventually, the car overheats so quickly when you turn the AC on.

Engine coolant temperature sensors are rare in this case, but I have seen many cars overheat when the AC is on for this.

Related: What Causes Car Shakes When AC Is On

2. Clogged Or Bad Car Radiator

The car’s radiator is a major component of the cooling system. The radiator helps the engine to operate effectively without overheating means the radiator eliminates excess heat from the engine.

When the radiator passes the coolant through the metallic fins to the engine, it helps a vehicle to operate at optimal temperature. But if the radiator work is disrupted, it leads your car to overheat when ac is on.

Over time the radiator can be clogged or blocked for debris. The radiator also can leak coolant. And the radiator fins can get bent or broken. But rust is the main culprit to make the radiator completely defective.

Whether you have a faulty radiator or defunct metallic fine in your car, it’s always a good idea to check the radiator, especially if you notice your car getting overheated when you turn on the air conditioning.

3. Water Pump Is Failing

As you already know from earlier, a water pump is a crucial part of a car cooling system that needs to be at an optimal state to operate the engine temperature.

The water pump makes sure coolant flows through the radiator, hoses, and cylinder head and block properly to maintain the car’s operating temperature.

A failing water pump will not be able to circulate coolant through the engine block. As a result, the car engine temperature will go up when AC is turned on or idle.

Bad water pumps not only overheat the engine, but it can also cause some particular engine damage for its long existence.

See Also: How To Remove Freon From Car At Home

4. AC Compressor Overload

ac compressor overload
AC compressor overload

The most common reason a car overheats when AC is on is the AC malfunctioning compressor overload. The car’s air conditioning compressor is responsible for transforming the refrigerant from gas to liquid.

When you turn the air conditioner on, the compressor needs to work with the engine, and the compressor moves the refrigerant cylinders to compress, which creates great pressure on the engine.

As we know, the car air conditioning system draws great power from the engine. And putting a high load on the compressor that the defective compressor can’t handle, eventually making your car engine overheat.

The excessive load can damage the AC compressor or make it bad, which can prevent AC from blowing cold air.

Car owners need to take extra care of their car’s AC compressor because an optimal compressor is necessary to operate the air conditioning in the car.

5. Clogged Condenser Fins

clogged condenser fins
Clogged condenser fins

Your car air conditioning condenser is a heat exchanger that reduces the temperature of the refrigerant, but the fins of the condenser’s job is to keep anything away from entering the condenser.

So, the fins of the condenser also need to be clean enough to pass the air effectively into the condenser.

A car’s AC condenser fins can get clogged with dirt, debris, and various elements.

But, when your car’s AC condenser fins are clogged, the condenser won’t operate at the optimal temperature of the refrigerant.

Appropriately, the air conditioning puts more load on the engine; hence the car overheats when AC is on and idle.

Related Also: How To Check Freon Level In Car

6. The Cooling Fan Is Not Working

The cooling fan, also known as the radiator fan, is a vital part of the car’s cooling system.

Depending on the speed of your car, the cooling fan ensures the engine stays cool in every situation.

The cooling fan is positioned between the radiator and the engine of a car. The convenience of position allowed the cooling fan to cool down the engine property.

To a failed cooling fan, cooling down the engine is not possible; hence it’s normal to see cars overheat when you turn the AC on.

You also need to be concerned about components of the cooling fan, such as the fan switch, cooling motor, fan clutch, and more, because any defective component will lead the cooling fan not to pass the airflow.

7. Bad Cooling System

The car’s cooling system operates by several components which are connected to air conditioning directly.

A car’s major cooling system components are freeze plugs, radiator, cooling fans, heater core, pressure cap, hoses, overflow tank, and water pump.

Above I talked about several major cooling system parts that can cause car overheating when AC is on.

The car’s air conditioning system and the cooling system’s components have a very significant role. The cooling system’s main purpose is to keep the air conditioner’s condenser at the right temperature level.

When you turn on the air conditioner that heats up, the cooling system cools this down and blows the cold air.

The condenser temperature will rise if any parts or components of the cooling system are clogged or blocked. Therefore, when the condenser heat gets too hot, this will lead the car to overheat when you turn the AC on.

The car’s cooling system components can go bad for corrosion or particles; hence, cooling system components should be in check.

With a radiator and water pump, ensure your car’s cooling systems components are working optimally.

That’s all, now you know what are the causes why a car overheats when AC is on.

Many people ask me about a specific model or brand car’s overheating issue when ac is on. A question like a car overheats when ac is on Honda Civic or Jeep overheats when ac is on. But all of the car’s air conditioning systems are the same.

Signs Of Car Overheats When AC Is On

signs of car overheats when ac is on
Signs Of Car Overheats When AC Is On

Coolant leaking, often engine shuts down, slow acceleration, and a warning on the temperature gauge are the most common symptoms of a car overheating when AC is on.

Here are the most common signs of a car overheating when AC is on:

  1. Car Engine Shuts Down
  2. Engine Making A Ticking Noise
  3. Coolant Leaking
  4. Car Is Slow To Accelerate
  5. Warning On Temperature Gauge
  6. Smoke Is Coming From Underneath Of Car’s Hood
  7. Odd Smell Coming From Car

1. Car Engine Shuts Down

If your car overheats, your car will automatically shut down, no matter what causes the issue.

But, when you turn the car’s AC on and suddenly the car engine shuts down, which indicates you have an issue in the car’s air conditioning system that makes your car overheat.

In most cases, the car would not turn on until the engine cools down. So, it’s necessary to reduce the temperature before starting the engine again.

2. Engine Making A Ticking Noise

Hearing ticking sounds from the engine is another symptom of a car overheating when AC is on.

Engine making ticking noise mostly because of uses of engine oil. So, you should check your car’s cooling system to see if the engine is making a ticking noise.

3. Coolant Leaking

Leaking of coolant is always bad for the car’s air conditioning, especially for the engine.

Coolant is a substance that is used to reduce the temperature of a car system. Coolant is the main chemical that air conditioning systems use to cool the air.

When coolant or antifreeze leaks from the car, the engine overheats so quickly.

4. Car Is Slow To Accelerate

The car is slow to accelerate because car overheating with AC on is a common issue.

For excessive engine temperatures, the car acceleration can sometimes fail. Hence, you need to take this matter seriously.

5. Warning On Temperature Gauge

Another common sign you are going to notice when a car overheats with AC on is a warning on the temperature gauge.

The car’s temperature gauge is responsible for measuring the temperature of the car’s engine coolant.

Your car’s normal temperature should be between 195 degrees and 220 degrees which you will see in your car’s temperature gauge. So, if your car’s temperature gauge reads higher than 220 degrees, that’s a sign of the car overheating with AC on.

6. Smoke Is Coming From Underneath Of Car’s Hood

One of the most traditional ways to know your car is overheating for AC is a cloud of steam coming out from under the car’s hood.

This way to indicate whether a car is hot or not is still a very useful way. So, whenever you see clouds of steam coming out from under the hood, you should check your car for overheating issues.

7. Odd Smell Coming From Car

The car’s interior and exterior parts are commonly made out of plastics. So, if you notice a burning rubber smell from your car, it is often a symptom that your car is overheating.

How To Fix Engine Overheating When AC Is On

solutions for car overheats when ac is on
Solutions For Car Overheats When AC Is On

Cleaning the car’s radiator, flushing the engine’s coolant system, and refilling the engine coolant are the simple solutions for your car that overheats when AC is on.

Here are some solutions when the car overheats with ac on:

  • Flush The Coolant System
  • Clean Your Car’s Radiator
  • Test The Water Pump
  • Put Water Into Your Car’s Radiator
  • Check The A/C Condenser Of Your Car
  • Top Up The Engine Coolant

Flush The Coolant System

Flushing the car engine’s coolant system will carry away the dirt and rust from the coolant system. The Flushing coolant system of a car also vacates the used coolant mixture from the radiator and replaces it with fresh coolant.

If you notice the car’s temperature gauge goes up when the air conditioner is on, you can flush the engine’s coolant system to keep the car from overheating.

Experts recommend flushing the coolant system or replacing the coolant mixture with fresh coolant every two years or 30,000 miles.

Clean Your Car’s Radiator

The radiator is the grand central station for an engine’s cooling system. And as I mentioned earlier, the radiator is the major component of a car’s cooling system.

If your car’s radiator has been clogged, this might be the main culprit behind the car running hot when AC is on. When the radiator has been blocked, the radiator cannot pass the antifreeze and water continually.

Try to check the radiator and keep the radiator clean regularly. It would be very helpful if you could sometimes clean the radiator’s internal pipes with tools.

Test The Water Pump

The water pump’s job is to keep the engine cool down with coolant. But, when the water pump cannot circulate coolant through the car’s engine, the engine is going to overheat.

By listening to noises, checking the air temperature, and several other ways, you can easily test the water pump to know whether it’s working or not.

Replacing or repairing a failing water pump will do better work with the car’s cooling system to keep the engine cool.

Put Water Into Your Car’s Radiator

The radiator needs water to operate properly. That’s why you should check the radiator regularly to see if there is enough water.

If you see the radiator is dry, then add distilled water to the radiator. The car’s water pump takes water from the radiator and moves it through the motor back to the radiator, where the cycle begins again.

Check The A/C Condenser Of Your Car

The car air conditioner condenser is positioned between the car’s grille and the engine cooling radiator.

It’s necessary to check the AC condenser if the car overheats when AC is on or idle.

Because if you see your car’s AC condenser is clogged or blocked, you need to clean the condenser so that this can condense the refrigerant from gas to liquid properly.

Top Up The Engine Coolant

Coolant (also known as Antifreeze) is a colored liquid that is mixed with water to help regulate your car engine during extremely cold temperatures.

It has been said a couple of times here that lack of coolant is the cause of car overheating. So, if you want to avoid car overheating issues with AC on, you should keep topping up the engine coolant.

What To Do If A Car Overheats With AC On In Traffic

what to do if car overheats with ac on in traffic
What To Do If Car Overheats With AC On In Traffic

Cars overheating with AC on in traffic is not unusual; this often happens, especially when a car is experiencing difficulty with the cooling system.

Here are the steps you need to follow when your car overheats with AC on in traffic:

Step 1: You Have To Pull Over As Soon As Possible

While you are driving, suddenly you notice the temperature gauge goes up when the air conditioner is on without thinking of anything, you better pull over your car.

Remember, the more you run the vehicle, the more the engine will overheat. Therefore, stop driving and pull over your car.

Step 2: Turn Off The AC Immediately

The best thing to do when a car overheats with AC on that is to turn off the car air conditioner in any situation.

Even if you are stuck in traffic, but your car engine is overheating for AC, just turning off the air conditioner will keep your car safe.

Step 3: Open Your Car’s Hood

Often when a car overheats with AC on, steam comes under the hood. That is why after pulling over and opening your car’s hood.

A most common practice to cool the car engine is opening the hood of your car, and this is a useful way.

Step 4: Turn Off The Engine With Ignition Switch On

After checking under the hood of your car, turn off the car engine but keep the key in the ignition as it should be on mode.

The reason behind keeping the ignition switch on is that this will keep the fan running, which helps the engine to reduce the temperature.

Step 5: Wait For Approximately 30 Minutes

From my experience, I found that an overheated car does not need over 30 minutes to cool down completely. So, leave your car for half an hour, then check the temperature of your car.

When your car engine is cold down, you need to check and search for any leakages in your car.

You can get help from roadside assistance to check your car properly and find out why your car overheats so fast and why your car overheats when the AC is on.

Can A Bad AC Compressor Cause Car To Overheat?

Yes. A car AC compressor can cause overheating of the car engine. If your car’s AC compressor has seized up, the belt will not be able to move properly.

The AC belt connects the AC compressor clutch to the engine crankshaft, which allows the compressor to be turned via the engine’s power when activated.

That’s why the car air conditioner belt is an important component. With a defective belt, you can drive your car, but the car will get overheated after a few miles.

When it comes to car overheating issues, you have to be aware of many parts of your car cooling system too.

Can Low Freon Cause Cars To Overheat?

A lack of or low Freon in a car can cause a car to overheat because when the Freon or coolant runs out, the car’s AC compressor can’t compress the Freon. 

That’s why air conditioning compressors produce excessive loads on the car engine; eventually, the whole car will overheat.

Can The AC Make Your Car Overheat?

Your car’s air conditioning can make your car overheat for defective AC components, which will make cars overheat.

Most importantly, your car’s cooling system has the significant ability to make your car hot.

So, if your car has faulty AC components, that can cause the car engine to overheat. 

Final Thoughts

The car’s cooling system’s defective components are the main cause of car overheating when AC is on.

Here, I have shared all of the possible reasons, symptoms, and solutions for fixing car overheats with AC on.

You should not consider the car overheating issue as a simple or minor problem. Car overheating issues are going to damage the engine, which can be very expensive to repair for you.

If you have tried all of the possible solutions in your car and haven’t got the proper solution, you need to go to a professional or auto service center to check the problem and get the solutions. 

As we already know, that car overheating issue can cost you a massive amount of money to lose. Also, car overheating can put you in great danger anywhere and anytime. So, you need to care about your car’s air conditioning to keep yourself and your family safe.

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2 thoughts on “Car Overheats When AC Is On: Causes, Symptoms, And How To Fix”

  1. Well … it’s takes about an hour of driving, then car will over heat . The air will stop blowing out of the vents, even though the fan is still working. Just got a brand new water pump and 2 thermostats , thinking maybe the first one had been faulty. Stuck in Fla. trying to get home . Yes I could take the windows and doors off the jeep and have redneck AC , but it won’t stop raining. Any ideas??

    • Hello Jessica,

      When a car stops blowing air even though the radiator fan is running, that is because the car air intake is clogged or blocked. So, I strongly suggest you clean the air intake and try to run the car and check.

      Thank you Jessica.


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