Blog Car Care Advice Car Overheating When AC Is On: 8 Causes You Should Know
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Car Overheating When AC Is On: 8 Causes You Should Know

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Does your car overheat when the AC is turned on? 
It could be your water pump, cooling fan, or the radiator acting up. 

Bottomline: An overheating car is dangerous, especially in traffic

That’s why we’ll help you understand the causes, solutions, and what to do if your car overheats on the road. 

This Article Contains: 

Let’s begin.

8 Causes of Car Overheating When the AC Is On

If your car begins to overheat, you’ll likely notice:

Most importantly, you could experience a sluggish vehicle, steam coming from under your hood, and your engine shutting down

Do these signs sound familiar?
Wondering what made your car overheat?

Let’s find out.

1. AC Compressor Overload

The AC compressor pushes refrigerant through the AC system to create cool air. An AC compressor overload happens from normal wear and tear or excessive strain.

Consequently, the hot AC places excessive stress on the car engine. This causes engine overheating.   

2. Defective Water Pump

The water pump forces coolant through the engine to maintain its temperature. It’s crucial for all the cooling systems of your car.  If it breaks, the engine temperature increases.

Turning the AC on then places an additional load on an already hot engine – overheating is imminent.  

3. Faulty Engine Cooling Fan 

The cooling fan draws air through the radiator and expels hot air from the car’s engine to keep it cool. Several problems can occur, including a broken fan motor, blown fuse, wiring issues, or a bad temperature sensor.

Basically, a faulty engine cooling fan causes higher engine temperatures. 

Combine this with the AC system, placing additional load on the engine, and you’ve got a recipe for overheating. 

4. Blocked Water Condenser Fins 

Condenser fins cool the refrigerant by transferring heat from the refrigerant to the surrounding air. 

Over time, these fins get clogged with debris, reducing the airflow created by the engine cooling fan. This limited airflow inhibits the car’s engine cooling.

5. Radiator Problems  

The radiator is an essential part of the coolant system. As cool air passes through, it absorbs heat from the hot coolant, reducing the coolant temperature. 

However, a clogged radiator (usually due to a debris buildup) interferes with the flow of radiator fluid (coolant), inhibiting heat transfer. This means the coolant isn’t cold enough to cool the engine effectively. 

Besides a clogged radiator, there are also other issues that can happen. The radiator fan can break, or a bad radiator cap may cause a coolant leak.  

6. Broken Thermostat

The thermostat regulates the engine temperature by controlling the coolant flow. Due to aging and corrosion, the thermostat can get stuck closed. Then, the coolant won’t reach the radiator where it cools. 

If the coolant remains hot, there’ll be nothing to mitigate engine heat. Any additional load the AC places on the engine could cause it to overheat. 

7. Bad Engine Coolant Temperature Sensor

The engine’s coolant temperature sensor tracks the engine’s operating temperature and relays this information to the ECU. If the temperature sensor malfunctions, the ECU receives inaccurate engine temperature data. 

In this case, it may not adjust the cooling system to reduce engine temperature. If you place extra stress on the engine by turning the car air conditioning on, it’ll likely overheat. 

8. Faulty AC Components

When car air conditioning components like the compressor, condenser, evaporator, or fan motor malfunction, they place an additional load on the engine system. 

The engine then has to work harder for the AC system to function, raising its internal temperature. If the cooling system isn’t able to cool off the engine to compensate, the engine overheats.

You now know why your car engine overheats with the air conditioner on. 
But what if it happens on the road? 

What to Do if Your Car Overheats in Traffic?

If you notice high readings on your temperature gauge, pull over as soon as you can and turn your air conditioner off immediately. Once you’re safe and stopped, you need to reduce the engine heat: 

It’s best to avoid driving before the overheating problem results in a complete engine stall, especially in hot weather. But sometimes, it’s not always possible, so let’s look at how to fix an overheating car. 

How to Address Car Overheating When AC Is On?

There are some simple options you can try to address the overheating issue, like maintaining the coolant level and topping up the refrigerant. 

However, it’s best if a professional mechanic takes a look. They would:

So, how much will fixing an overheating issue set you back? 

How Much Does It Cost to Fix a Car that Overheats? 

Mechanics typically charge between $75-$150 for the diagnosis.
However, there are also the repair or replacement costs to consider. 

Here are a few replacement estimates (excluding labor):  

Given the potentially significant expenses associated with certain replacements, it’s best to learn how to prevent engine overheating problems related to the air conditioner.

Keep reading!

How to Maintain Your Car’s AC System?

Here are some quick tips to keep your car’s air conditioning system in good condition:

Keep Your Car Cool with AutoNation Mobile Service

It’s best to avoid driving when you notice higher temperature gauge readings, especially in hot weather. 

If there’s an overheating problem with the air conditioning on, it’s likely engine cooling system problems coupled with the AC straining the engine. This can put you in danger on the road and damage your vehicle. 

So why not get a mobile mechanic to fix your car in your driveway? 
AutoNation Mobile Service is available seven days per week and offers a 12-month | 12,000-mile warranty on all repairs. 

Contact us for all overheating issues or any other vehicle assistance.