Why Is My Car Temperature High When AC On?

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Literally, the AC is supposed to keep the car at a cool temperature when turned on? That’s not so true. You may notice that your car heats up when the AC is turned on — and you’re probably asking, “why is my car temperature high when AC on?”

Well, this problem can be caused by issues not totally unconnected to your AC compressor and radiator fan(s). Before a car would overheat, one of the important components of the cooling system must have gone bad.

The cooling system is mainly the radiator and other components that connect to it. This article will explain the possible reasons why your car overheats when you turn on the AC.

Why Is My Car Temperature High When AC On?

What To Do When Your Car Temperature Gets High After Turning On The AC

This is caused by certain faults in the engine bay; it could be that the AC compressor is badly damaged, or the cooling fans are not working as expected. Below are some of the reasons that could cause your car to overheat when you turn on the AC.

1. Faulty Cooling System

When the cooling system is faulty, your car will overheat at every slightest action, causing a temperature rise. The condenser is part of a car’s cooling system.

When the condenser fins are blocked, or the fans stop working, there’s every possibility that your car would overheat when you turn on AC.

To solve this issue, have your car checked by a mechanic and replace the faulty condenser and/or its components.

2. Water Pump

The water pump is meant to help circulate coolant throughout the engine bay. When this circulation is not going on, it is possible for your car to overheat when you put on the AC or drive at low speeds. A water pump is also part of a car’s cooling system.

3. AC Compressor Overload

This is one of the common causes of overheating due to the AC being turned on. A faulty compressor puts more strain on the engine, and this can cause overheating – this is because the AC system utilizes more power (gotten from the engine) than many other components in a car.

When the compressor turns bad or faulty, turning on the AC would seem like you’re overloading the system; hence, it simply pushes more load to the engine, which could be the reason why you’re facing the issue. AC compressor is quite expensive to fix/replace.

4. Engine Coolant Temperature Sensor

You should consider this as the last thing to check if your car AC compressor, water pump, and condenser fans are all working well.

The engine coolant temperature sensor may be faulty and read a high temperature while your car is yet in perfect condition. To check/read this sensor, you need to use a temperature gun.

What To Do When Your Car Temperature Gets High After Turning On The AC

Why Car Temperature Goes High When AC On

Since the temperature increased after turning on the AC, you should turn off the AC immediately to check if the temperature gauge will return to its previous position. If the gauge returned, then you’re likely facing either of the problems explained above.

In contrast, if the gauge did not change, you should park and stop the car at a safe corner on the road. Wait for a while for the car to cool down (usually 30 minutes). Afterward, open the bonnet and check your coolant and radiator fan – these are the most typical causes of overheating in the engine bay.

When you check, and the coolant reservoir is filled up – plus, the radiator fan is working, then you need to call on a mechanic to check for leaks and other possible causes. It is a fallacy that overheating is normal when you turn on your car’s AC.


Hopefully, you now know why your car temperature is usually high when AC on. The four factors listed above are the most common reasons for such temperature change. However, there are other things and conditions that could have caused the temperature to rise.

If you hadn’t checked up on your car before this happened, it might just be that your car is requesting to be serviced. Also, if you could not detect any fault (as per the recommendations slated out here), ensure to get a professional auto mechanic to troubleshoot and fix the issue.

Again, overheating is not normal, whether caused by the AC or any other action/component.

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