Car Engine Dies or Shuts Off When AC Is On

Car Engine Dies or Shuts Off When AC Is On: Causes, Symptoms, and Fixes

The last thing you want when driving on a hot summer day is for the air conditioning to suddenly stop working in your car (AC). Unfortunately, many car owners deal with this problem regularly. If it occurs while you’re driving down the highway, it can be dangerous in addition to being annoying. The causes of this problem, warning signs to watch out for, and solutions will all be covered in this article.

Understanding the Causes

Low oil pressure is one of the most frequent reasons for an engine to shut off when the air conditioner is on. Oil is necessary, as you are aware, to keep your engine lubricated and cool. The engine won’t be able to operate properly if the oil pressure is too low, and it may shut off to protect itself. A malfunctioning oil pump, worn bearings, or a clogged oil filter are typical causes of low oil pressure.

The possibility of overheating also exists. The engine is strained by the AC compressor, and if the cooling system isn’t functioning correctly, the engine may overheat and shut off. Overheating may be caused by a damaged radiator, a broken thermostat, or a low coolant level in the system.

When the AC is on, electrical problems can also cause the engine to shut off. The engine may run out of power and shut off due to a failing alternator or battery. It may also be challenging to restart the engine after it has shut off if the starter motor is malfunctioning.

Vacuum leaks can also result in the engine cutting out. When one of the hoses has a hole or tear that allows air to leak into the intake manifold, there is a vacuum leak. The air-fuel ratio is thrown off, which makes it challenging for the engine to function properly. Additionally, vacuum leaks can make it challenging to restart the engine after it has been turned off.

Recognizing the Symptoms

The engine will shut off when the AC is turned on, which is the problem’s most obvious symptom. The engine may also be difficult to start after it has been turned off. A problem may also be indicated by warning or error messages on the dashboard, such as the check engine light. Finally, you might experience decreased acceleration and power.

Diagnosis and Fix

Diagnosis and Fix bad car ac

Checking the engine oil pressure is the first step in the diagnosis of this problem. You can use an electronic oil pressure gauge that connects to the vehicle’s diagnostic port or a mechanical oil pressure gauge. Low oil pressure is an indication that the oil pump, the bearings, or the oil filter are malfunctioning.

Next, check the temperature of the engine. If it’s running hot, there might be an issue with the thermostat, coolant system, or radiator.

Additionally, you should examine the charging system. Check the functionality of the starter motor, alternator, and battery.

In the end, look for vacuum leaks. The amount of vacuum in the intake manifold can be determined using a vacuum gauge. You will observe a decrease in vacuum pressure if there is a leak. Damaged hoses and a malfunctioning vacuum pump are frequent causes of vacuum leaks.

Fixes can range in complexity from something as straightforward as replacing a clogged oil filter to something more involved like replacing the vacuum pump, depending on the diagnosis. In any case, it’s important to deal with the problem right away to prevent expensive repairs and potential engine damage.

The Importance of Regular Maintenance

It is significant to remember that many of these problems can be avoided by performing routine maintenance. Your engine will run at its best if you check and replace your oil, coolant, and other fluids on a regular basis. Additionally, you can identify potential issues before they develop into significant problems by routinely inspecting hoses, belts, and other components.

Maintaining a healthy battery and checking the alternator’s performance are essential in the event of an electrical problem. When the AC is turned on, a battery that is not charging properly can cause the engine to shut off.

Additionally, it’s a good idea to have your cooling system checked out and cleaned if you notice that your engine frequently overheats or that your coolant level is dropping. This can lessen the likelihood of rust and sediment accumulating and creating issues in the system.


Overall, a number of problems, ranging from low oil pressure to vacuum leaks, can lead to an engine shutting off when the AC is turned on. You can take the necessary actions to identify and address the issue by being aware of the causes and identifying the symptoms. Keep in mind that stopping these problems before they start requires regular maintenance. It is advised that you take your car to a qualified mechanic who can properly diagnose and fix the issue if you frequently deal with this issue.