You are comfortably seated in your car probably running away from the simmering heat in order to enjoy the cool atmosphere that you would expect from the AC, you turn it on and suddenly realize that the car suddenly gets warm, by the minute. It gets into your nerves and starts wondering why your car would overheat when AC is on. You may find some comfort in the fact that you are not alone in this. You only become concerned when it starts to overheat even the Ac has been turned on for a few minutes, but when you turn it off, you get the normal room temperature.

When the problem becomes too persistent, you may have it to the extent that the seats start to be hot, you may have to ask yourself if any of the conditions below may be the reason why you are experiencing this.​


Reasons for Overheating​

1. Power Overload​

Sometime when the AC is on, it may draw a lot of power which in some cases may turn out to be more than it needs and thus overpowers the compressor which will eventually fail. When the compressor fails. It means that it cannot turn itself off and this, in turn, burdens the engine by consuming a lot of power which will lead to overheating.

2. Malfunctioning Cooling System​

This is the most common problem that results in car overheating When the AC is on. When the connecting tubes to the radiator start to wear out and are corroded due to rust. This can happen when the coolant has lost its anti-corrosion properties. When this happens, it renders the AC useless and starts to malfunction thus the heat.

3. Faulty Fan​

When the overheating on your car is directly proportional to the speed of the car, then you can make the assumption that the fan is faulty or not rotate at full speed. To make it clear, when the car is at a lower speed, there is less air flow into the engine which should turn the fan to provide the cooling effect expected. If this is the case you may have to use look at the fan for broken rotors and make a replacement if needed.​

3. Faulty Fan

4. Malfunctioning Temperature Sensor​

There is a remote chance that a temperature sensor is able to cause such overheating. But when caught up in this situation, it is a good practice to make sure that it works. To be sure, you may need to use a temperature gun to record the coolant temperature and make a comparison with the reading of the gauge. When the readings between the two components are not the same, this means that the AC is getting accurate readings and leads to overheating because the thermostat is not able to regulate the temperature properly.​

5. Not Enough Coolant or Antifreeze​

When the cat coolant runs low, the AC may fail to regulate the temperature because of the low levels of the coolant fluid. It is advisable that you check the levels of this fluid every two years. Periodic checks also safeguard the connecting tubes against untimely corrosion or rust. If the coolant stays for too long without being checked, some air may be trapped into the cooling system making it difficult for the AC to work as appropriate.

Note that sometimes using the wrong coolant will cause overheating of the car every time you turn the AC on.

5. Not Enough Coolant or Antifreeze​

6. Blockage on the Radiator​

When the radiator is blocked by flying debris, the best way to check this is by the use of pressure gauge which can tell if the radiator is getting and passing out the required amount of air necessary for cooling.​

6. Blockage on the Radiator​

Are There Solutions to This Problem?​

  • When the air conditioning fluid or gas used in your car is not the recommended one, it is advisable to check its compatibility and ask your mechanic for the right type of gas fluid. This is best done by a qualified mechanic because of the special tools used when diagnosing.
  • Installing an air pressure gauge to check air flowing into and out of the colluding system will help in clearing debris that may be stuck. If this does not solve the problem, you need to take your car to a specialist to check on the radiator before replacing it.
  • Regularly check the status of the anti-freeze liquid. Make it a habit of replacing the fluid every two years to maintain its consistency and make sure that rust does not build up on the tubing’s.
  • Once in a while, you can use the help of a qualified mechanic flush air that is trapped in the cooling system. This is done to ensure that pressure on the coolant gets back to normal.
  • Always make sure that your radiator has water and coolant up to the recommended minimum levels at all times.

TIP: make sure that when dealing with the radiator, you only open it using a thick cloth so that you do not get scalded.The coolant should be refilled when the engine is running to avoid blockage in the engine. When refilling the engine is not running can lead to severe problems.

What to Do When In Traffic?​

When the AC decides to misbehave when you are stuck in traffic may present a very uncomfortable situation. To avoid escalating the situation further, you can do the following as you head to the nearest auto shop.​

  • Engage the park gear or neutral and rev the engine to increase airflow to the fan.
  • Be gentle on the brakes. Applying 'hard' brakes causes a lot of friction which may lead to overheating.
  • You can adjust the AC dials in order to increase the blower speed to the maximum to increase air flow.


I am sure you do realize that this is a very common problem going by the problems listed above. The remedies listed are there to guide on trying to understand what could be the problem so that when you take the car for service you know what to tell the mechanic. Upon trying the above remedies and still the car overheats when AC is on, you need to take the car to the garage for deeper analysis.

Share your views and let us know about your experience, kindly use the comment section and share and let others know more about AC problem.​

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Chief editor at Paul's Gigantic Garage. I came up with this blog to help you to sort out some basic problems your car may be facing and in turn, save lots of cash by some of my DIY tips that I hope will get your car out of its current situation. I also had in mind motor enthusiasts who for the love of cars who are constantly looking for information about cars on the latest trends, questions, fixes, driving, tricks, and accessories.


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