Car Shuts off When AC Is Turned On: Causes and Fixes

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If your car shuts off when AC is turned on, it’s hardly ever the fault of the AC. Rather, it’s often an underlying fault with one of the core components of your car.

Car Shuts off When AC Is Turned On

In this article, our auto team reveals all the major causes of this problem and the best solutions. Here’s all the info you need to fix the problem!

What Are the Reasons Why Your Car Shuts off When AC Is Turned On?

The reasons why your car’s engine dies or shuts off when the AC is turned on include faulty IACs, faulty electronic throttle control, compressor problems, excess refrigerant, and damaged/worn belts. Sometimes, the cause is also traceable to a number of electrical problems in your car.

Your AC is killing your car likely because your alternator or voltage regulator isn’t working well enough to withstand the immense load it’s putting on the entire system. It’s possible you have a bad alternator or some other faulty component causing a deficiency in your car’s power/charging system.

– Defective IAC (Idle Air Control) Valve

A faulty idle air control valve can make your car shut down anytime you put on the AC. The idle control valve has the job of increasing or reducing the amount of air passing through the throttle valve (in other words, increasing or decreasing the air-fuel ratio) to regulate the rotational speed of your engine, especially when it’s idling. This prevents the engine from shutting down when extra load is put on it.

Causes of Car Shuts off When AC Is Turned On

Your car’s air conditioning system draws a lot of power, which is why the IAC valve always adjusts your engine’s rev/min (rotational speed) after you put on the AC so that your engine can carry the extra load. A faulty or damaged IAC will not be able to regulate the rev/min of your engine to produce the needed extra power, so your engine will shut down every time you put on the AC.

One common fault encountered with IAC valves is the accumulation of carbon and dirt over time. In some instances, however, they can also fail completely. One other sign you can use to know your IAC is bad is when your car backfires while driving.

– Electronic Throttle Control Has Malfunctioned/Failed

If the electronic throttle control (ETC) of your car has failed, you may find your car going off whenever you put on the AC while driving. Electronic throttle control is the substitute for IACs in modern vehicles.

Modern vehicles use the electronic throttle control system to regulate the airflow electronically. A typical ETC uses special sensors and software to determine the right time to open or close the throttle valve to regulate your engine RPM.

 

If you have a bad electronic controlled throttle body, your car will have trouble amping up the engine RPM when you put on your AC, as the valves won’t open to allow in the needed extra air. Usually, ETCs also face the problem of blockage by accumulated carbon, just like IACs. Excessive carbon will restrict the flow of air, even if the valves open. This will cause the shutting down of your engine any time more load such as AC is applied to it.

– Bad Compressor

A bad compressor is another possible reason why your engine shuts down or dies when you put on your AC. The AC compressor is responsible for converting the low-temperature-low-pressure refrigerant in your AC system into high-temperature-high-pressure refrigerant.

A bad compressor will consume lots of engine horsepower (10hp or more), reducing your engine’s RPM. This makes your engine stall or even stop.

Sometimes, a compressor may not be bad but just seized. Seized compressors are usually caused by a lack of lubrication and cause the same side effects as bad compressors. In some cars, a bad AC compressor will activate the check engine light.

– Stuck Compressor Bearings

Stuck compressor bearings can also make your car engine shut down every time the AC is turned on. The compressor bearings are what make the rotation of the compressor possible. Bearings get worn out with time, and they can also seize. If your compressor bearing fails, it ruins the entire compressor assembly and the spinning motion.

Bearing failures are one of the major reasons why AC pulleys get stuck. Issues like contamination, misalignment, corrosion, and lack of lubrication can cause bearing failure. Signs of failed bearings include high-pitched squealing and grinding or growling sounds.

– AC Pulley Is Stuck

When the pulley of your compressor is stuck, you’ll find that your car dies whenever you turn on the AC. The AC pulley is a component mounted on the engine block. It works with the V-belt to drive the compressor via a spinning motion. Pulleys get worn out over time and can also get stuck due to factors like lack of lubrication.

Car AC Pulley Is Stuck

Other times, it’s the clutch connected to the pulley that fails and stops it from working. Failed pulley clutches can be caused by blown fuses, bad coils, or wiring problems. If you find that your pulley spins freely by hand when your car is off but fails to work when you turn on your car, then your pulley clutch is responsible.

A bad or stuck compressor pulley will drag against the belt and make the rotation of the compressor very difficult or impossible. Under these conditions, your AC will draw much more power from your engine, putting a strain on it. As a result, your car will start jerking and stalling or may even shut down. A bad pulley will also cause strange noises (like whining, chattering, or squealing) to come from the engine or even trigger dashboard warning lights.

– Worn/Damaged Belt

A worn/damaged belt can be another reason why your car shuts off when ac is turned on. The drive belt works with the pulley to make the rotation of the compressor possible. Whenever you put on your AC, your engine’s RPM increases, and the drive belt has to work faster. If this belt is worn, it will slip and alter the RPM. A worn or damaged belt will make your engine’s revolutions per minute slow down so much that the car hesitates (stalls) or even shuts down completely.

– Too Much AC Refrigerant

Too much refrigerant can also be the reason why your car shuts down when the AC is on. The refrigerant is what makes cooling or heating your car possible. It is the liquid that passes through the compressor to undergo a transformation before being sent out through the vents as cold or hot air.

Car AC systems are designed in such a way that the refrigerant level shouldn’t be too low or too high. If it’s too low, the AC cooling/heating will be ineffective. If it’s too high, it’ll cause an extra load on the engine. This extra load can force the car to shut down.

– Car Electrical Issues

Electrical issues in your car can also be the reason why your car stalls or dies when you put on the AC. Issues like faulty wiring, bad fuses, and loose connections can make your engine stall or even go off when high-power components like the AC are engaged.

How To Fix Your Car When It Dies Every Time You Put on the AC?

To fix your car when it dies every time you put on the AC, you have to fix or replace the affected or damaged AC component. This may entail cleaning the IAC/ETC, changing the compressor/pulley, and replacing the drive belt.

– Check and Clean IAC Valve

Cleaning the IAC valve can solve your problem if carbon residue has blocked your valve. To clean the IAC valve, you need to get a carbon cleaner. You’ll find your IAC valve on the intake manifold. Once identified, remove all connected hoses, cables, and screws to free the valve.

After the valve is free, spray the carbon cleaner to remove dirt and grime before using a clean cloth to wipe away any residues. Finally, replace the hoses, screws, and cables. Note that if your IAC valve is bad, you’ll need to replace it.

– Clean ETC

Cleaning the ETC will stop your car from shutting down during AC use. You can find your throttle body between the intake manifold and the air cleaner of your engine. To clean your ETC, you’ll need a clean towel. However, ensure to disconnect your car battery as well as any other connected electrical wires before carrying out this fix.

– Change Compressor/Pulley Bearings

If a bad compressor is the cause of your problem, changing it will make your car function correctly. Compressor bearings can also be changed if you suspect they are the cause of your problem. However, due to the complex nature and positioning of these bearings, it’s best to change the compressor altogether.

Solutions for Car Shuts off When AC Is On

Will your car’s AC compressor cause engine issues if it becomes faulty? The answer to this question is yes. When your compressor is bad or faulty, your engine has to work overtime to power it. This can make your engine wear out or even break down.

– Change the Drive Belt

Changing the drive belt of your car will make your engine attain the right RPMs when you engage the AC, and this solves the problem of your car shutting down when AC is on. To change the drive belt, all you have to do is spin the drive belt tensioner, take out the old belt, and install the new one. A new drive belt can cost anywhere from $15 to $80.

– Check Refrigerant Levels

Getting your refrigerant to be at the right level can also solve your problem. If you have in-depth knowledge of how AC systems work and what kind of refrigerant your car uses, you can do this check yourself. Usually, you can tell when the refrigerant is too much via the pressure gauge. However, it’s best to get a professional to check your car refrigerant level for you and reduce the amount of refrigerant if necessary.

– Check and Fix Wiring, Fuses, and Spark Plugs

Carrying out simple electrical fixes in your car can make your car work well with your AC. Check and fix any faulty wirings and loose connections. Also, change bad fuses and plugs in your car. Fix any bad wirings or connections to the IAC’s electrical connector, and remember to check for any broken lines, especially those going to the IAC or ETC.

Car Shuts off When AC Is Turned On Solved

Can a Fluctuating Battery Voltage Cause a Car to Shut off When the AC Is Turned On?

A car’s AC system requires a steady power supply to function properly. Fluctuating battery voltage can disrupt this balance, potentially causing the car to shut off when the AC is turned on. By solving battery voltage fluctuations, you can ensure a stable power flow and prevent unexpected engine shutdowns while using the AC.

Conclusion

Having your car’s engine shut down every time you use the AC can be discomforting. Thanks to the knowledge from this article, you now know the various causes and solutions to this problem. For the sake of emphasis,

let’s go over the major points one more time.

  • A blocked/faulty IAC valve, Electronic Throttle Control (ETC), compressor, and pulleys are the most common things that can make your engine die when the AC comes on.
  • The problem could also be due to too much refrigerant or certain underlying electrical issues.
  • You can fix the ongoing issue by cleaning the IAC/ETC, replacing bad compressors and pulleys, changing the drive belt, or removing excess refrigerant.
  • Check and fix any loose fittings, bad fuses, plugs, or wrong wirings to help solve the issue.

If carrying out any fixes seems difficult or your problem persists after trying the steps listed above, see an auto mechanic for professional help.

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