{"id":3843,"date":"2024-11-08T08:02:11","date_gmt":"2024-11-08T16:02:11","guid":{"rendered":"\/wp-site\/?p=3843"},"modified":"2025-11-09T07:47:00","modified_gmt":"2025-11-09T15:47:00","slug":"car-overheats-when-ac-is-on","status":"publish","type":"car-repair","link":"https:\/\/jerry.ai\/car-repair\/car-overheats-when-ac-is-on\/","title":{"rendered":"Why Does My Car Overheat When the AC Is On?"},"content":{"rendered":"\n

One of the most common reasons why your engine overheats when your AC is on is a faulty engine cooling fan, fan switch, or fan motor. A bad engine coolant sensor, an overloaded AC compressor, a broken water pump, and blocked AC condenser fins can also create overheating issues.<\/strong><\/p>\n\n\n\n

On a hot day, your car\u2019s AC system could be doing a fine job keeping you cool and comfortable in the front seat\u2014but there could be a different story going on inside your engine. If you\u2019ve got the AC blasting and notice that your engine\u2019s temperature gauge is creeping up, you\u2019re probably scratching your head about what could be causing the issue.<\/p>\n\n\n\n

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Your engine is complex, so if you\u2019re feeling overwhelmed trying to pinpoint the root of the problem, let Jerry <\/a>lend a helping hand in this car repair<\/a> guide. The trustworthy brokerage app for finding great deals on car insurance is taking a look under the hood at some possible reasons your engine overheats when the AC is on and how to fix the issue.<\/p>\n\n\n\n

While we’re at it, we’ll even show you how to save on car insurance<\/a> costs.<\/p>\n\n\n\n

Reasons your car overheats when the AC is on<\/h2>\n\n\n\n

If you\u2019re completely stumped as to why your car overheats when the AC is on, below is a list of some of the most common causes of this particular kind of hot mess.<\/p>\n\n\n\n

Bad engine coolant sensor<\/h3>\n\n\n\n

The engine coolant sensor is a pretty self-explanatory part of your vehicle: its job is to monitor your engine\u2019s internal operating temperature. It reports the car\u2019s temperature to the Electronic Control Module (ECM), which (among other things) determines when to turn on your engine\u2019s cooling fans.<\/p>\n\n\n\n

If you have a defective engine coolant sensor, it will report an inaccurate internal engine temperature to the ECM. This can cause the fans to not turn on when they should, which can lead to your car overheating.<\/p>\n\n\n\n

Overloaded AC compressor<\/h3>\n\n\n\n

The AC compressor is an absolutely vital part of your car\u2019s broader AC system. Its job is to pressurize your engine\u2019s liquid refrigerant and draw power from your engine\u2019s output shaft in order to do so.<\/p>\n\n\n\n

If your AC compressor is malfunctioning, it puts what\u2019s known as a rotational load on the engine shaft, which in turn leads to your engine overheating.<\/p>\n\n\n\n

Defective water pump<\/h3>\n\n\n\n

A faulty water pump could also be to blame. It circulates a mixture of coolant and water throughout your engine in order to keep it at a healthy internal operating temperature.<\/p>\n\n\n\n

Without a working water pump, none<\/em> of your car\u2019s cooling systems will work\u2014which leaves both you and your engine uncomfortably hot.<\/p>\n\n\n\n

Bad fan, fan switch, or fan motor<\/h3>\n\n\n\n

Bad engine fans are one of the most common causes of why your car overheats when your car\u2019s air conditioning system is on.<\/p>\n\n\n\n

These fans aren\u2019t the ones that blow the cool air onto your face when you flip on your car\u2019s air conditioning system. Rather, they pay attention to your car\u2019s airflow in order to adjust their fan speed to cool the engine as needed.<\/p>\n\n\n\n

If the engine cooling fan is defective\u2014or if the fan blades are bent out of shape, the fan switch that triggers the fans to run, or the fan motor that powers them is not working\u2014then you can experience an overheating problem.<\/p>\n\n\n\n

Blocked water condenser fins<\/h3>\n\n\n\n

While AC condenser overload can cause your car to overheat, it\u2019s more likely there’s an issue with the condenser fins. If you\u2019re not familiar with the AC condenser, it\u2019s where hot refrigerant cools off to be distributed throughout your engine.<\/p>\n\n\n\n

A lot of dirt and debris can wind up stuck between the condenser\u2019s fins. When that happens, the AC condenser will not work as efficiently, and the coolant mixture will not be able to cool down as much. The result? Your car\u2019s engine will overheat when you turn on the AC system.<\/p>\n\n\n\n

What are the parts of air conditioning in cars?<\/h2>\n\n\n\n

Your car\u2019s HVAC system is notoriously complex. Reading about some of the parts above may have left you feeling a little mind-boggled, but don\u2019t sweat it.<\/p>\n\n\n\n

In general, your AC system works as a sealed, closed-loop system in which refrigerant is used to lower the temperature of the circulating air. So, if you\u2019ve got an overheated car, something in the coolant system has failed.<\/p>\n\n\n\n

Here\u2019s a brief rundown of some pivotal parts of your car\u2019s air conditioning system.<\/p>\n\n\n\n

Cooling fan<\/h3>\n\n\n\n

Powered by a fan motor, the cooling fans adjust their fan speed in tune with the internal temperature of the engine.<\/p>\n\n\n\n

When the internal temperature of your engine leans warmer and there\u2019s too much hot air, the cooling fans speed up. And, on the flipside, they slow down when the engine\u2019s temperature is closer to normal.<\/p>\n\n\n\n

Water pump<\/h3>\n\n\n\n

The water pump gets its power from your car\u2019s crankshaft. It\u2019s easy to get this part confused with an oil pump, but they are completely separate parts. An oil pump circulates engine oil to lubricate your engine, while the water pump pumps a coolant mixture into the radiator.<\/p>\n\n\n\n

Radiator<\/h3>\n\n\n\n

The radiator is a liquid-to-air heat exchanger that helps cool your engine. The radiator is made of a system of tubes (among other parts), that receives liquid coolant from the water pump. As the coolant mixture flows through the radiator, the radiator blows air across it to cool it down before it\u2019s released back into the engine.<\/p>\n\n\n\n

Thermostat<\/h3>\n\n\n\n

No, this one isn\u2019t the one that your dad wouldn\u2019t let you touch in your home. Your car\u2019s thermostat controls how often the coolant can \u201ccycle\u201d off and on in response to changes to your engine\u2019s temperature.<\/p>\n\n\n\n

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LEARN MORE<\/strong>: Does insurance cover engine failures?<\/a><\/p>\n\n\n\n

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How to fix an overheating engine when the AC is on<\/h2>\n\n\n\n

Check cooling system<\/h3>\n\n\n\n

And for this, we mean you should open the hood and take a look at your radiator\u2014a clogged radiator could be the cause of your overheating troubles. Take a look at the radiator hose and make sure it\u2019s free of any kinks or coolant leaks.<\/p>\n\n\n\n

But if those parts look fine, you should grab your mechanic\u2019s creeper, get under your vehicle, and check on the radiator cap. If you\u2019ve noticed that your radiator is steaming and fogging up your front windshield when you drive with your heater at full power, it\u2019s likely that your radiator cap is jammed shut.<\/p>\n\n\n\n

Refill coolant<\/h3>\n\n\n\n

Thankfully, this is an easy DIY fix. Low coolant levels are also one of the most common causes of why your engine is overheating. Locate your coolant reservoir and make sure that\u2019s filled up to the fill line. In many instances, topping off your coolant levels can fix the issue!<\/p>\n\n\n\n

Now would also be a good time to take a closer look at your coolant reservoir for any coolant leaks. If you spot any, you may have to get a coolant reservoir replacement.<\/p>\n\n\n\n

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Check refrigerant<\/h3>\n\n\n\n

We touched on your car\u2019s AC compressor system earlier, but it\u2019s worth revisiting here. When refrigerant inside of the AC system is not properly pressurized, your AC system has to work extra hard to lower the temperature\u2014which results in (you guessed it) your engine overheating.<\/p>\n\n\n\n

Have your air conditioner serviced<\/h3>\n\n\n\n

There\u2019s really only so much DIY diagnosing that you can do.<\/p>\n\n\n\n

If you\u2019ve checked out all of the parts listed above and still can\u2019t figure out what\u2019s going on with your AC system, it\u2019s time to take your car in to a professional.<\/p>\n\n\n\n

For this, we\u2019d recommend finding a mechanic that specializes or is certified to repair car HVAC systems. As we mentioned earlier, they\u2019re tricky beasts, and you\u2019ll need someone with the expertise and credentials to make sure you\u2019re fixing the problem.<\/p>\n\n\n\n

Get parts replaced<\/h3>\n\n\n\n

And, if all else truly fails, you may have to swap out a couple of parts if they\u2019ve become faulty. Exactly how much you\u2019ll have to shell out depends on the part you need to replace:<\/p>\n\n\n\n