Car Stalls When AC Is On (Causes and Fixing Ways)

A vehicle can stall and go off due to several reasons. However, if your car stalls when AC is on, it calls for immediate attention. The air conditioning system is designed to derive its power from a vehicle’s engine; hence, the possibility for the AC to negatively impact the engine.

You most likely rely on your car’s air conditioner during summer. So, imagine that your engine keeps stalling or dying when you turn on the AC. The experience can be so frustrating and unnerving.

Nevertheless, this article reveals the causes of such an occurrence and the solution to the problem. So, take a moment to read the content below if your car dies when AC is on.

car shuts off when ac is turned on

Causes of Car Stalls When AC Is On

There are various reasons why a car’s engine stalls when AC is turned on. While some causes can be easily fixed, others can be pretty expensive. The following are common causes of car engine stalling when the AC is on.

Faulty idle air control valve

A car’s idle air control valve is responsible for controlling the air required to maintain a car’s idle speed. It increases and decreases the vehicle’s engine rev/min to sustain the engine, especially when the vehicle carries a load. It acts as the vehicle’s throttle body plate.

Over time, carbon gradually builds up on the idle air control valve, making the component compromise the consistency of operations. Therefore, when the AC is on, the engine rev/min starts fluctuating up and down until it finally dies.

Bad electronic controlled throttle-body

Modern vehicles are designed with an electronically controlled throttle body that takes a signal from the ECM, like the idle air control valve. Also, carbon builds up on the component over time, restricting the air passageway.

Like the idle air control valve, the electronically controlled throttle body would fluctuate due to the restriction on the air passageway. When this occurs, the engine will most likely stall and go off when you put on the AC.

Overfilled AC refrigerant

Too much refrigerant in a car’s air conditioning system can also result in the engine stalling when the AC is on. This is because transforming the refrigerant will mount more pressure on the engine, thereby increasing the general load.

Therefore, when the AC is on, and the high pressure overburdens the engine, it will stall and go off. So, if your car shuts off when AC is turned on, check the refrigerant level.

Worn belt

The drive belt in a vehicle is responsible for rotating the compressor. Usually, when you turn on the AC, the engine’s RPM decreases because of the compressor. Meanwhile, a worn drive belt will eventually slip, fluctuating the engine’s RPM when AC is on.

As you drive, there’s a high tendency to experience hesitation or stalling until the engine ultimately shuts off. If your car loses power when AC is on, check the drive belt too.

Seized compressor

The compressor compresses the air conditioner’s cooling gas, increasing its temperature and pressure.

If the compressor experiences a jammed bearing, it will require too much power to rotate against the belt, causing surges until the engine dies down.

Electrical problem

Electrical problems such as a loose fuse or corroded relay can also make your car’s engine stall and go off when you turn on the air conditioner.

Most modern vehicles are designed with sensors that help to maintain safety by shutting off the engine in cases where severe damage is imminent.

How to Fix Car Shuts Off When AC Is Turned On

If your air conditioner turns on and off or constantly causes your car’s engine to stall and die when you turn on the system, carefully follow this guide to fix the issue, depending on the problem.

Fixing Car Stalls when AC is on YouTube

Turn off the AC and the engine

Firstly, turn off the AC and the car to avoid unnecessary damage before attempting to fix the issue.

Check the refrigerant level

Now, check the refrigerant level to verify whether or not the gas is low. This process can be sensitive; hence, you should contact an expert HVAC technician to check it out if you’re not a confident DIYer.

Clean the IAC or electronic controlled throttle body

If you notice that carbon build-up on the IAC or electronic controlled throttle body is responsible for the malfunction, carefully clean the component with a soft cloth dipped in a solvent.

Inspect/replace the compressor

The compressor is a significant part of your AC. So, carefully inspect the component for any signs of damage or general wear and tear. Then, fix minor damages (if any) or replace the faulty compressor where necessary.

Check the battery and alternator 

If the compressor and other AC components are okay, check your car’s battery and alternator for any faults that may be hindering an appropriate power supply to the engine.

Can A AC Compressor Stop A Car From Starting?

A seized air conditioner compressor will make your car’s engine very difficult to start, even if it does start in the end. The compressor is like the human heart in the air conditioning system.

The component derives its power directly from the engine. In other words, a seized AC compressor will prevent the engine from starting or cause it to stall, especially when the starting motor isn’t strong enough.


If your car stalls when AC is on, the system is most likely battling with one or more causes outlined above. Nevertheless, do not panic if this is your experience. Instead, carefully inspect or diagnose the AC system to determine the exact problem.

After that, ensure to fix whatever the issue may be. However, while some faults can be easily rectified, others can be money and time-consuming. Meanwhile, contact a professional auto technician to handle the job if it seems too technical.

Finally, AC problems, as well as most automotive issues, start with minor malfunctions that result from poor or inconsistent maintenance. So, kindly resolve to imbibe a routine and consistent maintenance culture henceforth.


Mr. Shafiqule Islam is a graduated Mechanical Engineer and has more than 15 years experience of repairing and maintenance of different brand vehicles like Toyota, Mitsubishi, Ford, Mercedes, BMW etc. He is also giving training to Mechanics. He has started writing to share his practical knowledge to Vehicle Owners, Drivers and Mechanics to keep their cars at best fit.

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