Why Does My Car Alarm Keep Going Off?

If your car or neighbor’s car alarm keeps going off in the middle of the night, you’ll know how frustrating and unnerving it is. I don’t joke with my sleep; whatever disturbs me while sleeping is “hell on earth” for me.

Two nights ago, I slept very late, around 1 am, and my car alarm kept going off soon after. It was frustrating because it happened three to four times that same night. If you cherish your sleep so much like me, I won’t wish that to happen to you. But why does my car alarm keep going off that night?

Some of the common reasons car alarms keep going off are a low or dead battery, lousy key fob, wiring issues, incorrect installation, oversensitive sensors, and malfunctioning sensors like door sensors, trunk sensors, shock sensors, and hood latch sensors. Consult a mechanic to fix the issue if you can’t resolve it.

In this article, I’ll explain the possible reasons why car alarms keep going off, the pros and cons of car alarms, how to know if you have a car alarm, how to reset alarms, and how to disconnect them. But first, let’s see the importance of alarms in cars.

how to stop car alarm from going off

Importance of my car alarm

The car alarms are designed as a safety feature in cars, and it has many benefits.

Avoid car theft

Crimes happen in every city, no matter how strict the laws are. It can happen to anyone, even when you least expect it. Car theft are one of the crimes that keep increasing every day.

As car theft rates increase in most cities, auto manufacturers start equipping their vehicles with car alarms. The solemn purpose is to discourage car theft. A car alarm is always active but silent. It makes noise whenever it detects someone trying to make an unauthorized entry to your car.

Hence, car thieves will prefer to go for cars without an alarm to reduce the chances of getting caught.

Insurance policy

Another significant benefit of having a car alarm system is your insurance policy. If you own a car without an alarm system, your premium insurance will be higher. Some vehicles feature system components that insurance companies put into consideration.


Some car thieves are determined in their operations. Nothing can scare them off, even the blaring car alarm. That’s why some car alarms feature immobilizer that prevents the car from starting whenever the alarm is set off.

The old system of hot wiring a car with the intent of stealing it will not work on vehicles with immobilizers unless the burglar locates and disconnect the immobilizer. This explains why almost all expensive cars feature immobilizers.

Peace of mind

A car with an immobilizer will give you peace of mind since the alarm will set off whenever a burglar attempts to enter or steal the vehicle. Even if you are not around to hear the alarm sound, you’ll be assured that the immobilizer in the alarm system will lock up the steering and the engine from starting.

Protect expensive properties

Even if you don’t own one of these cars that are generally a target for car theft, it can attract a burglar. While we advise people not to keep expensive properties and essential documents in their cars, some do it anyway. Your vehicle may not attract car thefts, but your GPS units, radio, expensive property, or essential documents can attract thieves.

Your car alarm can help protect these properties because the thieves won’t want to risk getting caught. However, do not risk keeping essential documents in your car unless there’s no other option.

Tracking capabilities

If your alarm system does not feature an immobilizer and the burglar succeeds in stealing the car, he’ll not take it too far. You can report to law enforcement agencies to track the vehicle if the alarm system has a tracking capability. Some tracking features in car alarms can connect to your smartphone and has a kill switch that shuts down the car. The car theft may escape, but you will recover your vehicle.

How do I know my car has an alarm?

Most folks who own a car with advanced factory features like keyless entry presume their vehicle has an alarm system. That’s not always the case. Hence, you should double-check before concluding. Here are two common ways of checking if your car has an alarm system.

Check the owner’s manual and the key fob.

The owner’s manual is the manufacturer in print. It’s like asking your manufacturer if your car features a factory security system. Flip the pages on security, and you’ll see if the vehicle has a factory alarm system installed. However, the manual won’t tell you if there’s an aftermarket security alarm installed in the car. Hence, this method is only helpful for checking factory security alarms.

You have a security alarm if your vehicle has an aftermarket key fob. These aftermarket key fobs feature car alarms. Most aftermarket dealers will have a key fob as a secondary key, separate from the original one.

Attempt a break-in

Another way of checking if your car has a security alarm is to attempt a break-in. This may sound odd, but believe me, it is the surest way of finding out if you have a factory or aftermarket car alarm installed in your car.

  • Wind down your car windows.
  • Take off the key from the ignition and leave the car
  • Lock your car with the key fobs while the windows are still rolled down
  • Wait for a minute or two
  • Step out, drop the key far from the car, and try opening the doors from the open windows.

If there’s a security system installed on the car, the alarm will sound as soon as you open the door from the inside. This method works on both aftermarket and factory car alarm systems. If the alarm doesn’t sound, repeat the steps one or two times to reconfirm.

Find the alarm under the hood.

If you want to check the type of car alarm your vehicle uses, you have to open the underhood and see the type of alarm you have. I recommend having a mechanic check the alarm hardware. If they see the alarm system, they can tell you how it works and the functions of different features.

Why does my car alarm keep going off?

Car alarms can go off for several reasons, like a dead battery, weak alternator, malfunctioning key fob, blocked or damaged sensors, oversensitive sensors, writing issues, faulty control unit, or incorrect installation.

Dead battery

This may sound eccentric, but a dead battery can prompt several odd behaviors. As I said earlier, my car alarm disturbed my precious sleep two nights ago. The alarm repeats three to four times that night. It was the last one that I ignored for long.

The following day, I found out that my battery was dead. Here’s the thing, the alarm kept blowing due to a bad battery, which drained the remaining electric juice left inside.

The only solution was replacing the battery, and the nuisance hasn’t repeated. However, if you’re asking why does my car alarm keep going off in the middle of the night and I can still start my car in the morning without any hesitation, you have something else. It would be one of the following possible causes.

Malfunctioning key fob

The key fob, also called a remote key, is an electronic device used in locking, unlocking, and starting the car without touching it. All you need to do is to press the button on the remote. Your vehicle has a receiver unit installed in it. The receiver unit receives and processes the command on the remote.

If the key fob malfunctions, it may send a wrong signal that could sound the alarm. A malfunctioning key fob typically needs replacing or resetting the battery to work optimally. In some cases, you may have to reprogram the key fob.

Malfunctioning sensors

The car alarm system works with various sensors in your car. So it makes sense that if your Ford car alarm keeps going off, you have a malfunctioning sensor. Of course, this can happen to any car make and model.

A lousy trunk or door sensors are the common reasons car alarms keep going off. Also, newer modern cars have a hood latch that tells the car alarm system when someone tries to force open the hood. If this sensor becomes faulty, it can set off the car alarm even when there’s no burglar.

Oversensitive sensors

Aside from trunk and door sensors, your car can set off alarms with shock sensors. Shock sensors have different levels of sensitivity. Some of these sensors can trigger the car alarm even if a dog runs and badge the car.

You can adjust oversensitive sensors yourself or contact your dealership to adjust the sensors.

Lousy alarm control module

Most alarm systems have a control module. Hence, it is common to have a lousy alarm control module.

The control module comes with both factory and aftermarket car alarm systems. If your Nissan car alarm keeps going off and on, you likely have a lousy alarm control module.

Wiring issues

The car alarm system, including the key fob, uses electricity, and this electricity runs through wires. If any corresponding wire gets damaged, opened, shorted, or burnt, it’ll affect the car alarm system in different ways. It could cause the car alarm going off but no lights, or it could cause the alarm to go off and on. Wiring issues are quite challenging to diagnose but are easy to fix once you track where the damage is coming from.

Incorrect installation

If your aftermarket car alarm keeps going off right after installing it, there’s a high chance something is not properly hooked up. It could be a missed car sensor, crossed or open wire. Contact the installer to check if things are correctly hooked up.

Having seen all these possible causes, I know you would be wondering how to stop my car alarm from randomly going off. I’ll explain that in the following few paragraphs.

How do I reactivate my car alarm?

While the car alarm system reduces the chances of stealing your car, it can go bad and become a nuisance in your neighborhood or workplace. Luckily, all you need to fix the alarm issues is to reset it.

Here are the methods and steps of how to reactivate car alarms.

Method 1

As explained earlier, one of the reasons car alarms keep going off is a key fob or remote key issue. If the key fob stops sending signals to the receiver in the car, the alarm in your baby ride will keep going off and on.

Step 1: Visit your owner’s manual

Some car owners’ manuals will show how to reset the car alarm. So, consult your owner’s manual and see if you’ll find reset instructions. The reset procedures vary from car to car. However, you can try removing and reinstalling the remote battery.

Step 2: Reset the alarm using a scan tool

Most newer model cars have instructions in the car manual on how to reset the alarm system using a scan tool. Check the manual and follow the instructions there.

Proceed to the following method if this one doesn’t reactivate your car alarm system.

Method 2

Some car alarm reactivation approaches don’t need to visit your manual and can be deployed in a few minutes.

Step 1: lock and unlock the doors

Lock and unlock the doors with the manual key. The alarm will usually stop sounding once the system notices you have the manual key.

Step 2: Start the vehicle

If locking and unlocking the doors doesn’t fix the problem, insert the key into the ignition and start the vehicle.

Step 3: Use the manual key

If inserting the key into the ignition doesn’t stop the alarm from going off, come out of the vehicle, insert the manual key in the door, and lock and unlock the door. Do it twice, and it may stop the alarm from going off.

Method 3

Every electrical system in your car gets power from the battery. You may have to disconnect the battery if the alarm system keeps sounding. However, you must be cautious when applying this method.

Step 1: Locate the car battery

The car battery is a big rectangular box with two terminals, usually black. However, the top could have a black, green, yellow, or red label. Open your car bonnet and find the battery.

Step 2: Disconnect the battery

Take a sizable wrench, loosen the fastener, and disconnect the negative battery terminal. Keep the wire safe and ensure it doesn’t touch the terminal.

Step 3: Reconnect the terminal

Let the car sit for three to five minutes after disconnecting the terminal. Now, grab the disconnected cable and reconnect it. When you disconnect the terminal, it will prevent all electric flow from entering the car, including the ones that control the car alarm.

Method 4

The truth is there are several ways of reactivating the car alarm system in cars. If you don’t prefer any of the methods above, try disconnecting the fuse that controls the car alarm.

Step 1: Find the fuse box

Most cars have two fuse boxes, one in the engine bay and the other underneath the steering wheel. Locate the fuse box underneath the steering wheel. It is usually close to the vehicle diagnostics port.

Step 2: Take off the car alarm fuse

Read the diagram on the fuse box cover to determine which fuse is for the car alarm. Remove the fuse once you locate it.

Step 3: Change the alarm fuse

Check if the fuse is burnt and replace it as needed. Ensure you replace the alarm fuse with a fuse of the same amperage. The color of the fuse doesn’t matter, but it must be the same style and amperage.

How to disconnect my car alarm

If the car alarm keeps disturbing you even after reactivating it, you may have to disconnect it permanently.

Here’s a simplified instruction on how to disable car alarm permanently. However, kindly note that disconnecting your car alarm means removing one of the safety features in your car. Therefore, it’s important to make an informed decision before disconnecting it.

Step 1: Visit your owner’s booklet

The owner’s booklet may contain information like the wires to disconnect when dealing with your car alarm. Depending on your car make and model, you may only find this information in your vehicle-specific service manual.

You can also find this information online. However, you have to ensure you’re working with directions specific to your car.

NS: Ensure you disconnect your negative battery terminal before removing any other wire in the car.

Step 2: Disconnect the siren alarm control unit wire

Disconnecting or cutting the wire that goes to the alarm control unit will permanently disconnect the alarm until you fix it. Don’t remove other alarm components if you don’t know your onions.

Pros and cons of car alarm

Before you permanently disconnect your car alarm because it keeps going off, you should know its pros and cons. Also, if your car has no alarm, learn the pros and cons below before installing one.

Pros of car alarm

  • It features immobilizers
  • It features tracking capabilities
  • It gives peace of mind
  • It reduces the rates of car theft
  • It reduces premium insurance costs.


  • It can be expensive, especially if you opt for a more advanced one with more features.
  • It lacks response because it needs the owner or nearby individual to act before it stops the alarm.
  • It has limited effectiveness because advanced car thieves can jam or bypass the alarm.
  • It often gives a false alarm.
  • Over time, people will become desensitized to their sound due to false alarms, making them less effective.

Final words

At this point, you’ll no longer ask, why does my car alarm keep going off? Several factors like a dead battery, faulty sensors, malfunctioning key fobs, incorrect installation, wiring issues, oversensitive sensors, and lousy alarm control modules are the common reasons car alarms keep going off.

This article covers how to reactivate the alarm system, how to disconnect it, and the pros and cons you should consider before taking each action.

Whatever action you want to take, to disconnect or reactivate the alarm system, follow the above instructions religiously to get a good result. However, if you’re not a DIYer, contact your local mechanic or dealership to check and address the underlying problem.



While growing up, I knew I had a thing for car repairs though my parents never wanted me to learn mechanics. I always visit a mechanic garage in my small neighborhood after school. As I grew older, at age 16, I got addicted to anything automotive. My parents had to enroll me in that mechanic garage since giving up was never an option for me. As a dedicated mechanic who got into the industry from an early age, I'm graced with an addiction to diagnosing and rectifying automotive problems with ease.

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