6 Reasons why your car overheats when AC is on + solution (2023)

Has it ever happened to you that your car was running fine, but as soon as you turned on the air conditioning, the temperature gauge went over the allowed limit? Indicates that your car is overheating when the air conditioner is on.

It is normal for some cars to reach a high temperature for a short time with the engine running and the air conditioning compressor on (more power is required from the engine to compress the refrigerant). But when the compressor is off, it should not get hotter than normal.

Why is it happening? Before you can understand this, prior knowledge about two things is required. One is your car's air conditioning system and the other is the coolant system.

Air conditioning system in modern cars

Cars often have their own interpretation of an air conditioner that works much the same in terms of cooling, but may not have all of the additional components that a full-fledged AC system would.

The main components are the compressor, condenser coils,expansion valve, evaporator coils and receiver/drier. All these components operate on the same basic principle of the refrigeration cycle.

The air conditioning system is a closed, closed system that uses a refrigerant to "condition" the air inside the vehicle.

The compressor changes the low-pressure gas from the evaporator into a higher-pressure gas that can be moved through the system under pressure. It then goes to the condenser coils and releases its heat to the condenser coils outside the heated space.

The refrigerant then passes to the expansion valve, where it undergoes a pressure drop and becomes a low-pressure liquid that is sent back through the evaporator.

These common components work together to cool you down by removing moisture from the air inside the vehicle. In the summer, humidity is a hot commodity that can make your car feel much hotter than it actually is when it comes to how "comfortable" you feel in the car.

Cooling system of a car

Before we dwell on why a car overheats when the A/C is on, you should understand how a car's cooling system works. Overheating of the car is a direct result of a malfunction in the cooling system.

In a car, different components work together to regulate the temperature in the interior. The cooling system works with these components to maintain a constant temperature during summer driving and avoid the extreme heat that can potentially damage your car.

Cooling fan

The cooling fan focuses on the airflow of the car so that it can speed up or slow down depending on the temperature of the engine. This ensures that the engine is cooled at all times. The cooling fan speeds up when your car's interior gets hotter than normal and vice versa. It ensures that the engine is cooled at all times so that it does not overheat.

Water pump

Ofwater pumpin cars is the engine's drive unit, driven by a belt from the crankshaft. This pump supplies water to the cooling system and does not affect the engine oil lubrication, which takes place in a separate oil sump.

The pump has a filter through which the coolant passes before it enters theradiator.

The fluid in your car's engine is maintained by a pump that gets its energy to work from the pressure created by the motion of rotations caused by the rotation of the engine.

Radiator

A liquid-to-air heat exchanger, often referred to as a radiator, is one of the simplest ways to remove waste heat from an engine.

A liquid coolant flows through tubes in the radiator and the coolant gives off its heat to the incoming air as it passes over fins that extend into the air stream. The air is then expelled from the rear of the car and the coolant is returned to the engine.

The engine coolant is a mixture of water and ethylene glycol or water and propylene glycol. So the fluid that goes back to the engine is a mixture of these two chemicals in a certain ratio.

Thermostat

The thermostat is a part of your car's cooling system that works to maintain the engine temperature. The thermostat responds to changes in coolant temperature by controlling how often the coolant system is allowed to "cycle" on and off.

If the thermostat fails, it may open too quickly or stay open too long, causing the engine to overheat.

Why does my car overheat when the AC is on?

If your car overheats while the air conditioner is on, it could be for the following reasons:

1. Faulty engine coolant sensor
2. AC compressor overload
3. Faulty water pump
4. Faulty fan, fan switch and fan motor
5. Clogged condenser fins

Let's explain these reasons a bit:

1. Faulty engine coolant sensor

The job of the coolant temperature sensor is to keep track of the engine's operating temperature. The ECM (Electronic Control Module) uses this information along with outside air and intake temperatures to determine critical engine parameters. The ECM cannot function properly without the coolant temperature sensor.

If the engine coolant temperature sensor fails, it reports the wrong coolant temperature to the ECU. As a result, the operation of the cooling system is affected and you may notice that the engine overheats when the air conditioning is on.

2. AC compressor overloaded

A compressor is the backbone of the car's air conditioning system. The main task of the compressor is to increase the pressure of the refrigerant. A failing ac compressor would not be able to do the job correctly.

The ac compressor draws power from the output shaft of the motor. When the compressor fails, it exerts a rotating load on the motor shaft. An increased engine load is the basis for engine overheating.

Therefore, in this scenario, you need to look for a mechanic and have your ac compressor repaired.

3. Faulty water pump

If your car regularly overheats when the A/C is on, it could be due to a weak or faulty water pump. The coolant pump's job is to keep the engine warm. This is done by pumping the coolant mixture into water jackets around the engine compartment.

A bad coolant pump results in an incompetent cooling system. If the engine cooling system fails, you will not get cool air into the cabin of the car.

So if your car overheats when the air conditioner is on, you need to check the health of the pump.

4. Faulty fan, fan switch and fan motor

Cooling fans provide smooth heat transfer between the engine coolant and the outside air. When your car's cooling fans aren't working properly, you're going to have overheating problems.

A defectengine fan is also the main cause of engine overheatingwhen the air conditioner is on. The car air conditioning system puts additional strain on the engine. As a result, the heat is generated at higher speeds.

The cooling system has to work even harder to dissipate the excess heat. When the supporting part, such as the cooling fan, fails, the chances of the car overheating are multiplied.

Several problems with cooling fans can cause the car to overheat. For example, the blades of the fan may have become deformed. Or the fan switch responsible for turning on the fan may have failed. Similarly, cooling engine failure can also be the culprit.

5. Clogged condenser fins

AC condenser is the part where hot refrigerant loses its heat. This causes cooling. If your car overheats when the A/C is on, it could be a direct result of a condenser malfunction.

But a more common reason is that dirt and debris get stuck in the fins of the condenser. If the fins on the condenser are clogged, the heat transfer process would not be as efficient.

This puts extra pressure on the air conditioning, resulting in an overheated engine.

How to fix motor overheating when AC is on?

If your car overheats when the air conditioning is on, there are several ways to prevent this. You should follow the advice below and most likely your problem will be solved.

Check the cooling system

If you think your car's engine is overheating, the first thing you should look at is your cooling system.

There are several parts to your cooling mechanism, but we'll focus on the radiator and hoses here for our purposes. Your radiator must be in good working order and not clogged. The hoses must be flexible and free from leaks, etc.

If you've checked your cooling system and it's still overheating, the next thing to do is get under the hood of your car and take a look at your car.radiator dop.

If you see steam coming out of the radiator before it reaches the top of the engine bay (i.e. in front of the windshield) and if you drive slowly for a while with your heater on full blast, it probably means that your radiator cap is stuck and not working properly.

Top up coolant

Usually the problems related to the cooling of the car are caused bylow coolantlevels. All you have to do is check the coolant in time and top it up as needed. Do this and you can prevent the car from overheating.

If your coolant level is lowered more than usual, that's what you need to docheck for coolant leaksalso. If a leak is found, flush out the old coolant, fix the leak and pour in the new coolant.

Check coolant

If your car overheats with the air conditioning on, you should check the refrigerant pressure in your car's air conditioning.

If sufficient refrigerant pressure is not maintained, the air conditioner has to work extra hard to reach the desired temperature. It draws more power from the motor shaft, which can cause the car to overheat.

Service air conditioner

Have your air conditioner serviced if your car overheats while the air conditioner is on. Timely maintenance eliminates the possibility of clogged condenser fins, clogged radiator, low refrigerant or coolant level and many such problems.

So if your car overheats when the air conditioning is on, rest assured that it is not due to the above problems. You have to look beyond this range.

Replacement of parts

If none of the above solutions do the job for you, the only viable option left to you is the replacement of potentially faulty parts. You can try replacing the following parts to prevent the car from overheating:

• Replace AC compressor - $1,200 - $3,500
• Replacement AC condenser fan - $200-$900
• Water pump replacement - $200 - $1,300
• Coolant temperature switch (sensor) replaced - $100-$500

Any of these replacements can solve your car overheating problem.

Conclusion

Any car will overheat if the coolant system is not working efficiently. If your car overheats when the air conditioner is on, it could be for several reasons. But it would come down to one thing. That is that turning on the AC had added pressure to the output shaft of the motor.

The increased rotational load also caused an increase in engine heat generation. The cooling mechanism was unable to dissipate this excessive amount of heat. And this resulted in an overheating car.

Apparently car overheating can be caused by a faulty water pump, abad coolant temperature sensor, clogged radiator, clogged condenser fins, a faulty cooling fan motor, or a faulty ac compressor clutch.

Most of these problems are solved during the inspection of the cooling system and the maintenance of the air conditioner. Keep your coolant and coolant levels up and prevent cooling problems in your vehicle.

Frequently Asked Questions

Can your air conditioning overheat your car?

Yes, your car's engine can overheat when the air conditioner is on. It is mainly due to the ac compressor drawing power from the motor shaft. This means extra pressure on the engine.

If more power is generated in the engine, more heat is lost. Now the cooling components may not be able to dissipate this excess heat, causing the car to overheat.

Why does my temperature gauge go up when my air conditioner is on?

As mentioned above, the car engine can also overheat when AC is turned on. However, you shouldn't just rely on the temperature gauge going up. A temperature gauge can also go up due to a faulty coolant temperature sensor.

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

It is usually due to a faulty cooling fan. Because the cooling fan is responsible for improving heat transfer between hot coolant and outside air. If the idle is bad, no air blows past the radiator and condenser fins. As a result, the car overheats.

What Are the Symptoms of a Bad AC Compressor?

If the compressor of your car's air conditioning system is faulty, you may experience the following symptoms:

1. The car's engine failed
2. Ticking sounds come from the engine compartment
3. Temperature gauge goes up
4. Strange smell from the cabin
5. Slow acceleration