Common Reasons Your Car Shuts Off When AC Is Turned On?

An effective AC system in the car will maintain the cool temperature in the car. AC doesn’t only maintain a cool environment, but it also filters the air which is quite important in polluted cities. This protects you from hazardous air pollution and health issues. What if your car shuts off when ac is turned on?

In this article, we’ll be discussing some common reasons behind the engine stalling issue.

Why Does The Car Stalls When AC Is Turned On?

Many car owners notice when they turn ON the AC, the engine starts to hesitate or shake, or sometimes the car stalls. It is a very common problem that happens in a car when the ac is turned on. The car shuts off when the AC is turned ON, which means that the load on the engine is High and the power produced by the engine is Low.

The AC consumes a lot of energy when it is turned ON and on the other hand. If the engine cannot produce more energy. The engine will jerk/hesitate and will shut OFF. The engine compensates for the lack of power through a mechanism of an idle air control valve to increase its power and speed.

When the engine idles and the car doesn’t move, we call it that the engine is in idle mode. Normally the car’s Idle RPM is from 600 to 1000 RPM depending upon the car and outside temperature. At this RPM the engine produces enough amount of power to stand smoothly without stalling.

Whenever a load is put on the engine such as turning ON the lights or turning ON the AC. It sucks a lot of power and the engine can not produce more power at the same RPM. It must increase its RPM to generate more power and stand smoothly.

Can A Bad AC Compressor Cause A Car To Stall?

The air conditioning system requires power from the engine. So there is no question that the air conditioner would put some pressure on the engine. If this will not be controlled, this can cause some overload or malfunction.

One example is the regulation of the idling rotational speed through the IAC or the idle air control valve. This is also referred to as the idle air sensor control motor because of its function. The valve will also determine the amount of air that will bypass the throttle plate in a vehicle that is fuel-injected IC., and it will change the idling speed.

So a fault in the IAC such as a build-up will produce a poor idling or stalling of the engine. If this is not working correctly, the engine might not cope with the loads produced by the different systems.

What Are The Symptoms Of A Bad AC Compressor?

These are the symptoms if you have a terrible AC compressor.

1. Lack Of Hot Air Released Outside:-

The compressor will take hot air from the inside of the home and then release it outside if it is working correctly. So you can tell if your compressor has a problem when you hold your hand near the fan on the AC unit and if the air is not hot but lukewarm or cool.

This is a sign that your compressor might be having problems. This can also mean that the unit is not correctly compressing your gas. This can be a sign of a leak in the refrigerant.


2. Loud Or Strange Noises From the Unit:-

If your compressor is in good condition, it will start properly, and the unit will also start smoothly. You will hear the compressor and the fan of the compressor appropriately.

So if the unit will make a vibrating sound or make a rumbling noise or even a sound popping or banging, this can mean that it has potential problems. This can mean that the CA compressor has electrical problems.

3. Failure Of The Compressor To Turn On:-

If your AC is not cooling the area anymore, you have to check the condensing unit of your home. Then, you have to replace it or have it repaired.

Here are some symptoms of this problem of engine stalling when AC is turned on.

Does AC Affect the Speed of a Car?

No, the AC will not affect the speed of the car. Even though the engine power is shared between the car and the AC, the car has sufficient throttle power to manage both the speed and the AC system at the same time.

1. Modern engines are equipped with the ability to manage both the AC and engine systems in parallel.

2. An alternator or a battery can help give out power to the AC when the clutch is engaged.

3. The maximum speed of the car as well as the acceleration might decrease when the AC is switched ON. However, if you are driving at a constant speed, it will not be affected if you switch ON the AC.

If you notice that the speed of the car is affected when the AC is switched ON, you can get the car calibrated. This can help balance the load better. Some models have automatic calibration while most of the older models don’t.

Does AC Affect Engine Power?

Yes, the AC uses power from the engine, which reduces the power available for the drive.

1. The AC uses up more fuel when driving with the windows down. Hence, this affects the mileage of the engine.

2. The AC and the engine share the throttle power and hence the AC will reduce the acceleration capacity of the car.

Every car has an ideal fuel speed range. If you follow this speed range, you can reduce the loss of fuel efficiency.

What Are The Reasons Behind Your Car Shuts Off When AC Is Turned On?

Most people notice that their car surges at idle. When the car AC is turned ON, and at the end, the engine shuts OFF. It happens due to many reasons, but it is preferred to know the reasons why the car shuts off when the AC is turned ON.

1. Faulty Idle Air Control Valve:-

This is the most common reason the engine dies when AC is turned ON. Idle Air Control Valve increases and decreases the engine RPM not to shut off the engine when a load is put on the car.

With time the carbon builds up on the idle control valve, through which it cannot perform well. As a result, the engine RPM fluctuates up and down and finally, shuts off. So, clean the “Idle Air Control Valve (IAC)” with a soft cleaning cloth dipped in a solvent.

2. Bad Electronic Controlled Throttle Body:-

The electronically controlled throttle body is also a common reason for the engine dying when the AC is turned ON. Modern vehicles do not have an “Idle Air Control Valve”, they have an Electronic Controlled Throttle Body also called Drive by Wire. It takes a signal from ECM.

The same phenomena can happen with Electronic Throttle Control (ETC) Body. If carbon builds on it, It will restrict the passageway for more air to enter and as a result, the car stumbles. So, do a regular tune-up to clean your car’s electronic throttle control body.

3. Seized Compressor:-

The compressor is an expensive reason for a car to shut OFF the engine when AC is turned ON. The seized AC compressor causes the car to stall. The compressor squeezes the refrigerant under high pressure and uses the power of almost 5 to 10 horsepower. It is enough amount of energy to drop down the RPM.

Sometimes, your compressor may be seized due to a jammed bearing, which takes too much effort to rotate against the belt causes surges, and finally, the car shuts off. You have no option other than to replace the compressor.

4. Stuck Compressor Pulley:-

Often a compressor is in good condition but its pulley bearing is stuck. This stuck pulley bearing drags against the belt and becomes very stiff to rotate the compressor. And put too much strain on the engine, which leads to car jerking and stalling.

5. A Worn Belt:-

The drive belt rotates the compressor. When a compressor is turned ON, engine RPM decreases. A worn drive belt with compressor ON will slip causing a fluctuation in RPM. This increase and decrease in RPM are known as car surges or hesitations, which leads to shutting OFF the car.

6. Overfilled With AC Refrigerant:-

This is another reason for the car dying when AC is turned ON. The refrigerant in the AC system should be neither high nor low in amount. It must be in the right quantity. AC system with overfilled refrigerant causes overpressure on the engine and forces the car to stumble when AC is turned ON.

7. An Electrical Problem:-

An electrical problem is also the most common reason a car shuts off when AC is turned on. Often the car surges due to electrical problems. Make sure you don’t have a loose fuse in the fuse box or corroded relay.

Therefore, these are some common reasons for the issue of the car shuts off when ac is turned on.

How To Fix Your Car Shuts Off Issue When AC Is Turned On?

A short circuit in the AC system can cause the car engine to stall or turn OFF when the AC is turned ON. This can be fixed by identifying the exact component causing the problem and taking the necessary action.

You can fix the issue of the car turning OFF when you try to switch on the AC by following these simple steps:

1. Use a fuse puller or tweezer to remove the AC fuse. This will most likely disconnect the AC unit from the engine.

2. Unplug the AC compressor. This will reduce the load on the engine and thereby prevent it from shutting down.

3. Replace the idle air control (IAC) from the car. Note the error code and refer to the manual to fix the issue.

Your AC is taking a lot of energy from your engine. It will require power. Have your mechanic check the components of your vehicle. As mentioned, there are a lot of reasons why you have this problem. You have to identify the problem first. You can do the checking on your own. But if you want, you can also consult an expert.


We hope the above-mentioned information about your car shuts off when ac is turned on will be helpful to all the readers. If anybody’s doubts persist feel free to comment in the comment section below. We’ll definitely try to solve your doubts as soon as possible.

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