What Triggers A Car Alarm? (7 Different Factors)

A car alarm system is an essential component that keeps your vehicle safe from vandalism, and knowing how your alarm works is vital to help you disarm it. So, what are some of the things that trigger your alarm? If you’d like to find out, keep reading!

What Triggers A Car Alarm?

Car alarms are triggered by motion or movement around the vehicle. Depending on their sensitivity level, they can go off if someone touches the car, if the sensors are triggered, if the vehicle has a low battery or when you’re trying to open the door. As well, your alarm can also be triggered by bumps or vibrations.

If you’d like to learn more about what sets off a car alarm,keep reading this article for more useful facts and tips!

What Sets Off A Car Alarm?

Car alarms can be triggered for a number of reasons, such as the reasons listed below:

1. Someone Touches The Car

Your car alarm is designed to keep your vehicle safe from theft. Therefore, when someone accidentally hits your vehicle when the alarm is set, it will go off automatically.

For cars that have sensitive sensors, the alarm goes off when people pass close to the vehicle, either in the neighborhood parking or a public parking space.

If your vehicle is in a public space, this can be a noise nuisance, especially if the alarm keeps going off.

2. Pets

2. Pets

Vehicles with strong motion sensors will be easily triggered by pets such as cats and dogs, which is a common concern for car owners who have pets.

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If a neighbor’s pet accidentally touches your tires or any part of the car, the alarm will go off. This is a false alarm and can be quite irritating if you have pets in your neighborhood. To prevent this recurrence, it’s better to switch off the motion sensors and adjust your sensors.

3. Opening The Door With A Key

Most cars have a remote key fob that you can use to arm and disarm the alarm system, meaning you can control the alarm and avoid it being a nuisance.

If you use a key fob to close the car and then use a key to open the car, your alarm will be automatically triggered.

4. Activated Sensors

Your car alarm system has different types of sensors, and each of these has a distinct function and trigger. These sensors include the following:

Shock Sensors

Shock sensors are the most common because they detect when someone is moving or trying to break into your vehicle.

Single-stage shock sensors will detect when the door is being forced open or your window is breaking. On the other hand, dual-stage shock sensors go off with the slightest impact, such as vibrations from a stereo system or an animal jumping, so it’s common with false alarms.

Voltage Sensors

Voltage sensors monitor the amount of static voltage in your electrical system. If there’s any voltage drop, the alarm will be triggered and go off when the door or the trunk is opened.

Door Sensors

Door Sensors

These door sensors are activated when the door, trunk, or hood is opened, which is an effective way to protect your belongings.

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Motion Sensors

Some thieves will jack up your car to try and remove the wheels. However, if your vehicle has motion sensors, they will go off to warn you.

Motion and tilt sensors detect when the vehicle is being rotated or tilted and will send a signal to the control unit and set off the alarm. These sensors are less likely to give a false alarm if someone accidentally bumps into your vehicle.

5. Low Battery

A low or dead battery also triggers a car alarm, as it’s very common for the battery to drain overnight. Apart from being a safety feature, the car alarm is also installed to warn you about your battery.

Therefore, if your battery is dying, your car alarm will be triggered as a warning. You can use a tester to measure the voltage to confirm if this is the issue.

6. Malfunctioning Key Fob

6. Malfunctioning Key Fob

Your car comes with a remote key fob to lock and unlock the doors. When it’s faulty, the key fob has controls that are connected to the alarm system that sends the wrong signal.

When this happens, your batteries might be the problem. Therefore, to fix this, you can replace the batteries or reprogram the key fob.

7.   Faulty Hood Latch Sensor

Modern car models have a hood latch that comes equipped with sensors that will set off the alarm when you open the bonnet.

If your hood sensors are functioning properly, they will detect when the hood latch is open and will show a warning light on your dashboard.

When your sensors are defective, the car alarm goes off automatically. These sensors malfunction because of dust and dirt that accumulate around them.

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To know more, you can also see our posts on what is a passive alarm, how much is a car alarm, and how long do car alarms go off for.


Car alarms get triggered by motion or movement around the vehicle. Your alarm will go off if somebody touches the car, sensors get activated, a faulty key fob, low battery, or when someone is trying to open your door. 

Some alarm systems have a higher sensitivity level; therefore, they can be easily triggered by slight movements such as bumps or vibrations from a stereo system.

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