Why Does My Car Overheat When The AC Is On? (9 Reasons Why)

Have you ever encountered a situation when your vehicle ran without any issues, but when you switched on the air conditioner, your car’s temperature gauge went over the safe range? You know it’s a sign your vehicle has a problem.

However, why is this happening when the AC’s role is to provide coolness, not heat? Want to know why? Then, look what we found out about the matter!

Why Does My Car Overheat When The AC Is On?

Your car overheats when turning on the AC because of a faulty AC compressor, raising engine load, and is among the most frequent reasons for a car to overheat. Additionally, an ineffective cooling system is another. So, whenever the air conditioner is on, your vehicle may overheat because the air conditioner compressor increases your engine’s rotational load.

If you want to learn more about why your car overheats when the AC is on, here are nine reasons. Continue reading!

1. Faulty Engine Coolant Sensor

Your car’s coolant temperature sensor is responsible for monitoring the engine’s operating temperature.

Further, coupled with the air temperature level outside and the intake temperature is used by the ECM, or Electronic Control Module, to calculate necessary engine settings.

So, the ECM won’t function efficiently by not having the coolant temperature sensor.

That said, if your car coolant temperature sensor malfunctions, it will inform the ECU of the inaccurate coolant temperature.

As a result, your coolant system’s functionality is impaired, and you may notice that your car engine overheats while the air conditioner is on.

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2. AC Compressor Overload

The core of your car’s air conditioning is a compressor. With that, the primary function of the compressor is to boost the refrigerant’s pressure.

Of course, a malfunctioning AC compressor can hardly do the task effectively. So, the engine’s output shaft provides power to the air conditioner compressor.

As a result, the engine shaft experiences rotational stress whenever the compressor malfunctions. Thus, engine overheating is caused by increased engine pressure.

3. Defective Water Pump

If your vehicle frequently overheats when the air conditioner is running, the problem may be with your car’s water pump.

Generally, the coolant pump’s responsibility is to keep the engine at a constant temperature. So, water jackets across the engine compartment are pumped with the coolant mixture.

Further, an ineffective cooling system results from a defective coolant pump. When your engine cooling system malfunctions, you won’t have access to cold air in the car’s interior.

So, if your automobile overheats while the air conditioner is running, you should examine the pump.

4. Damaged Fan

The efficient passage of heat from the engine coolant to the outside air is ensured by cooling fans.

Therefore, you will have overheating issues when your vehicle’s cooling fans are not functioning correctly.

So, engine overheating whenever the air conditioner is on is frequently caused by a malfunctioning engine fan.

Of course, the car’s air conditioning system exerts an additional load on the engine, and heat is being produced at greater rates.

As a result, the coolant system must work even harder to remove the extra heat.

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Therefore, the likelihood of an automobile overheating increases when a supporting element, such as the cooling fan, fails.

5. Clogged Or Blocked Condenser Fins

Clogged Or Blocked Condenser Fins

The part of the air conditioner’s condenser where heated refrigerant loses heat causes cooling to happen.

So, if your automobile overheats while the air conditioner is running, the condenser malfunction may be to blame.

However, debris and dirt entangled in the condenser’s fins are a more frequent cause. Naturally, the efficiency of the heat conduction would be reduced if the condenser’s fins were blocked.

As a result, the air conditioner is under additional pressure, which heats the engine.

6. Clogged Radiator

Overheating may result from obstructions or interferences in the radiator’s internal pipes, which may impair air flow and coolant flow.

Generally, it is a collection of materials like dirt, rust, etc. However, leaks might have a role.

7. Incompetent Overall Cooling System

You should check the cooling system if your vehicle overheats whenever the air conditioner is on.

Usually, the cooling system functions to maintain the condenser of the air conditioner, which warms up when the AC is turned on.

So, blocked condenser fins, a broken condenser fan, or a malfunctioning water pump that does not effectively distribute the coolant might all blame the overheating.

In addition, the corrosion that develops in the radiator pipes may be caught by the coolant system, inhibiting the proper coolant flow.

8. Defective In-Vehicle Parts

Your vehicle may overheat whenever the AC is on due to faulty parts.

Of course, when the condenser, compressor, refrigerant, and evaporator malfunction, pressure enters the air conditioner, raising the temperature inside the vehicle.

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Therefore, you should frequently examine these parts to ensure they are functioning correctly to prevent these problems.

Also, you must remember that even a small malfunctioning part might cause issues with your vehicle.

9. Damaged Air Conditioner

A poor or malfunctioning AC might cause your car to overheat when the AC is on.

Also, if your AC isn’t working correctly, you’ll discover that the vehicle engine becomes too hot, the dashboard will get hot, and the seat may get hot a few minutes after the AC is turned on.

But, when you switch off the AC, your automobile immediately returns to its average temperature, which is a sign of an issue with the air conditioner.

To know more, you can also read our posts on why your engine sound so loud after rain, why your car whines when you accelerate, and why your car leaks water.


Cars usually overheat when the AC is on because of the ineffective operation of the cooling system, such as the condenser and the water pump of the air conditioner.

Therefore, your vehicle overheats when the AC is on because both generate too much heat.

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