7 Reasons Your Car Stalls/Shuts Off When AC Is Turned ON

Car AC Stumbles When The 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.

If your car shuts off when you turn on the AC, you’re not alone. Many car owners have experienced this problem and have had to take their car to a mechanic to get it fixed. This is a frustrating experience, especially on a hot day. There are a few reasons why this might happen. In this powerful guide, you will learn seven crazy reasons why the car shuts OFF when AC is turned ON.

Related Post: How Car Air Conditioner Works

Car Shuts OFF When AC Is Turned ON

Car Shuts OFF When AC Is Turned ON
Car Shuts OFF When AC Is Turned ON

Many car owners notice when they turn ON the AC, the engine starts to hesitate or shake or we can say vibrate, and sometimes the car stalls (means shuts off). This is a very common problem that happens in a car when the ac is turned on.

In simple words, I want to help you understand. 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. Here I am breaking down the topic in simple words. It is a fascinating topic, just stick with me.

As you know, AC is a huge energy sucker. It consumes a lot of energy when it is turned ON and on the other hand, if the engine can not produce more energy, then the engine will jerk/hesitate and finally will shut OFF. The engine compensates for the lack of power through an idle air control valve mechanism to increase its power and speed.

The car manufacturer introduces the valve “Idle air control valve” in a manually operated throttle body to compensate for power. But, the important question is what is the meaning of idle? Here is the definition of the term “Idle”.

Engine Idling

Throttle Body With Electronic Idle Air Control Valve
Throttle Body With Electronic Idle Air Control Valve

When the engine is running and the car is not moving, we call it 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.

According to the research, the Air Conditioner causes about a 30-40% average decrease in driving range in Hybrid Electric vehicles.

Now come to the “Idle air control valve (IAC)”.This valve increases and decreases the air-fuel ratio to regulate engine idle RPM. When the AC is turned ON, the valve opens to flow more air into the engine, increases Its Idle RPM, and also produces more power and vice versa. So, when carbon builds on the “Idle Air Control Valve (IAC)”, it will fail to maintain proper idle, and as a result, the car surges and shuts OFF when the load is put.

Electronic Throttle Body
Electronic Throttle Body

Sometimes a defective “Idle Air Control Valve (IAC)” or “Electronically Controlled Throttle Body” will send wrong input data to the ECM. The ECM miscalculates the input which leads to a bump in the idle speed and activates the car stumbling.

So, clean the “Idle Air Control Valve (IAC)” and “Electronic Control Throttle Body” with a soft cleaning cloth dipped in a solvent or do a regular tune-up.

Related Post: 11 Reasons Your Car Air Conditioner Blows Cold Then Warm

7 Crazy Reasons Car Stalls When AC Is ON

Below are the seven reasons why the car shuts OFF when the AC is turned ON.

  1. Faulty Idle Air Control Valve
  2. Bad Electronic Controlled Throttle Body
  3. Seized Compressor
  4. Stuck Compressor Pulley
  5. Worn Belt
  6. Overfilled With AC Refrigerant
  7. An Electrical Problem

1. Faulty Idle Air Control Valve

Idle-Air-Control-Valve
Idle-Air-Control-Valve

This is the most common reason the engine dies when AC is turned ON. The 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

Electronic Controlled Throttle Body
Electronic Controlled Throttle Body

The electronically controlled throttle body is also a common reason the engine dies 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

Seized Compressor
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 causing surges, and finally, the car shuts off. You have no option other than to replace the compressor.

Related Post: 7 Basic Parts of Car AC System (With Pics) & Their Functions

4. Stuck Compressor Pulley

Compressor Pulley
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 is. And put too much strain on the engine, which leads to the car jerking and stalling.

Related Post: How To Fix Car AC Compressor Clutch Not Engaging

5. A Worn Belt

Worn Belt
Worn Belt

The drive belt rotates the compressor. When a compressor is turned ON, the 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

Overfilling With AC Refrigerant
Overfilling 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.

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7. An Electrical Problem

Corroded Relay
Corroded Relay

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 a corroded relay.

Related Post: Car Relay Guide

Frequently Asked Questions (FAQs)

Does the AC compressor affect the engine?

The short answer is Yes, The AC compressor affects the engine. The compressor is the heart of the air conditioning system, and it has a direct impact on engine performance. The compressor circulates refrigerant throughout the system, and it helps to cool and pressurize the refrigerant.

The AC compressor is driven by a belt connected to the engine crankshaft. When the AC is turned on, the compressor puts an extra load on the engine, which can slightly reduce fuel economy and increase emissions. In addition, If the compressor is not operating properly, it can cause the engine to overheat, and it can also affect the performance of the air conditioning system.

Can a bad AC compressor cause a car to stall?

A bad or seized AC compressor can cause a car to stall if the compressor is not functioning properly. This can happen for a variety of reasons, such as if the compressor is not receiving enough power or if the compressor is not properly lubricated. If the compressor is not working properly, it can put a strain on the engine, which can lead to the car stalling.


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