Why Does My Car Overheats when AC is On

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During hot summer days in the car while stuck in traffic, the AC is the only source of relief stopping you from going full Mad Max Fury Road. But in a very plausible nightmare scenario, you may end up not being able to turn it on. For a very simple reason. Every time you turn the air conditioning on your car engine overheats and may eventually even stop running.

Unbearable as this situation is, it is actually a very common issue especially for older cars and trucks. However, there are solutions to this problem and no it does not involve you having to replace your entire AC assembly or even your car. In this post we will help you find the root cause of this issue and what you can do to potentially remedy it without having to spend a fortune on repairs you don’t really need.

The answer lies in the complex relationship between the AC and engine systems which are very heavily interdependent. Let us we delve deeper into this topic by looking at signs, symptoms and possible causes that are associated with this issue.

Signs of an Overheating Car

There are several symptoms that your car may display when it is about to overheat. These include, but are not limited to: 

Temperature gauge

You will notice this from a mile away. Your temperature gauge will be showing an increasing temperature in your car engine. It does not take a genius to know that if the temperature is rising then you need to stop doing whatever it is that is causing this increase or you could end up with a very expensive repair bill on your hands.

Car feeling physically hot

Your car is physically hot! You can feel the heat emanating from your hood, there may be steam or smoke coming out of your tailpipe and if you open up your hood and find that the temperature of your car engine is high enough to burn you should consider stopping what you are doing and allow it to cool down.

Ticking sounds from the engine compartment

If there is a loud and repetitive ticking noise coming from your engine compartment this could be a sign of damaged or burnt out engine parts. The engine oil that lubricates your engine parts will generally burn up starting from the bits of it that are closest to the exhaust system. If it is not too late you should pull over as soon as possible and investigate what’s going on inside your engine bay.

Engine shut down

This happens as a last resort when your car reaches critical temperature and shuts down as an emergency safety measure. If this happens do not panic, it is very common and there are usually no lasting effects other than for you to be stuck where you are or wherever you were headed.

When your engine overheats and does not cool down it can cause irreversible damage that in some cases is not worth repairing. Therefore, it is important that you find the root cause of your engine overheating problem and resolve it before it gets out of hand.

Strange odor

Your car is also emitting very strange odors that are not normal for your engine. These could range from rotten eggs to burning plastic and in many cases the stench will be overwhelming. This means the seals or gaskets that are preventing toxic engine fumes from escaping into your car cabin are either damaged or no longer working. Therefore, avoid driving in this condition until you have fixed the problem.

Speeding issues

Many times as a direct result of your car engine overheating you will notice that your car is unable to accelerate. This is because the excess heat in your engine bay breaks down the thermal resistance of the cylinders causing combustion issues and impeding the normal function of the pistons within them.

A cloud of steam

Almost like your engine telling you that this is the final straw, if you notice a cloud of steam coming out from the hood of your car this indicates that you have a very serious problem on your hands. It is the result of two separate issues which are coolant boiling over and oil burning up near the exhaust system.

Reasons Why Your Car Is Overheating When AC Is On

If you are experiencing your car overheating when the AC is on there are a few possible scenarios to consider. 

Faulty Air Conditioner

This may sound a bit silly but it is true, if your air conditioning system is broken then this will result in the engine overheating. In turn, this causes your AC to work harder thus putting even more strain on the engine

Problem with Radiator

If the radiator in your car is cracked or damaged it can lead to overheating when the AC is turned on. Coolant may leak out of the radiator at an increased rate and if this coolant hits the hot exhaust system it will cause smoke to rise from under the hood. 

Clogged Radiator or Faulty Fan

If this occurs your AC will not be able to work as efficiently as it should and this will once again result in overheating. It also explains why the engine is overheating when the AC is turned on along with the car not being able to cool down.

Compressor Overload

An AC that is experiencing problems can overload the compressor and this will cause it to overheat. Usually, the compressor has an adjustable pressure relief valve that allows it to handle a certain amount of heat before shutting down for safety reasons. However, if you have been driving with your AC on constantly then there may not be enough coolant in your system to keep the compressor cool. Even if you do add more coolant to your AC this will not prevent the compressor from overheating.

Inadequate Cooling System

The cooling system in your car consists of the water pump, radiator, overflow tank and hoses. If any of these components is not working at its full capacity then it will cause all sorts of cooling problems that can lead to overheating. For example, if the water pump in your car has failed or if there is a constant air pocket in your cooling system this will cause overheating when the AC is turned on. 

Bad Struts And Shocks

If you have bad struts and shocks in your car then it can cause overheating when the AC is turned on. Due to the lack of dampening effect, whenever you turn on the AC this will transmit additional vibration into the engine which makes it work even harder than usual.

Temporary Solution When Stuck in Traffic

Even though these problems require a professional to be addressed on a permanent basis there are some methods you can implement in an emergency.

1. Pull Over

The first thing that you should do when your car starts to overheat is pull over into a safe location. The last thing that you want is for your vehicle to break down in the middle of heavy traffic. If it is not possible to get out of the heavy traffic, then try and drive slowly until you can safely park your car.

2. Turn Off Car Air Conditioner

If you have experienced an increase in your engine’s temperature when the AC is turned on then you should immediately turn it off. This will help to reduce the strain that the AC system puts on your engine and hopefully prevent further damage from occurring.

3. Open the Hood of Your Car

When you open the hood, if you notice a cloud of white smoke billowing from underneath then this is a very bad sign. It indicates that your engine has been seriously damaged and that it may need to be replaced.

4. Leave the Car Engine Off, but Keep the Key in the Ignition

You should leave the engine off and let your car cool down to avoid overheating further. However, if you do turn the engine off too soon then it could lead to a reduction in oil pressure or a temporary shut down of the cooling system which will cause even more damage. Therefore, try and keep your car fan running for at least 15 minutes but not longer than that.

5. Check the Coolant Level in Your Car

Another solution is to make sure that your coolant level is at optimum levels. Topping it off normally this ensures that your car cools properly while you are stuck in traffic so that your engine does not overheat.

How To Fix Car Overheat

If you want to have a go at fixing the issue yourself then the following steps should help.

Clean Your Radiator

This is the most important part of your overall repair. If you are having problems with overheating but when using the AC then this is definitely something that should be addressed immediately. You will need to remove all debris from your radiator in order to get it running at its best again.

Install an Air Pressure Gauge

Another way to diagnose any problems is by installing an air pressure gauge inside the system. This will let you know if your AC compressor is healthy or not. If there are any leaks in the line, then this will also show up on the gauge before it causes further damage to your engine.

Flush the Coolant System

Doing so will help eliminate buildup in your cooling system. It will also help to ensure that you do not have any corrosion inside the plumbing of your vehicle.

Change the Coolant Mixture Every 2 Years

You should change the coolant mixture every 2 years to ensure that you do not have any blockages or buildups. If the system has been neglected for a long time, this can cause rust or corrosion to build up inside the pipes.

Add Water to the Radiator

A simple way but effective way is to make sure that your car’s radiator is topped up with fresh water. If you notice any traces of gray or white residue at the bottom, this means that your cooling system has been contaminated and needs to be flushed immediately.


In summary, you can try these steps. If your car still overheats when the AC is turned on, you should take it to a professional and have them work out what is wrong with your vehicle.

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