What Triggers a Car Alarm? Everything You Need to Know

A car alarm is one of the essential vehicle components that protects you from theft and vandalism. However, these devices can be set off by a variety of factors, many of which have little to do with danger and thieves.

In the sections that follow, we’ll go over everything that can trigger a car alarm, as well as give you tips on how to avoid unwanted noise.

How Do Car Alarms Work?

Generally speaking, car alarms are triggered by movement near the vehicle they are installed on. Thus, they will undoubtedly go off if someone touches the vehicle, tries to open the door, or break into it in any other way.

This fact is possible due to the various types of sensors that make up a car alarm. They range from motion sensors to those that respond to vibrations, meaning that they can truly catch any suspicious activity near your vehicle.

However, if an alarm consists of extra sensitive sensors, it can go off without anyone touching it. In other words, a stray cat can set it off, or a small bird flying by and coming close to your window.

Types of Car Alarm Sensors

To better explain how different car alarms work, we’ll cover them in a little more detail below.

Door Sensors

All car alarms, no matter how old or sophisticated, have door sensors. As their name suggests, these sensors pick up any activity related to your doors, especially concerning your locks.

So, if a thief tries to break into your car, the sensors will go off immediately. As a result, the alarm will start blaring, alerting you or anyone else close by that something is amiss.

It is important to note that these sensors usually cannot detect if someone breaks the window and opens your car door from the inside. This fact makes sense, as the sensors are responsible for the lock only.

Impact Sensors

Though door sensors cannot detect a window break, impact or shock sensors can do so within seconds. As you can probably already guess, these sensors pick up on any hits or forceful breaks that occur on the vehicle.

Now, these sensors can fall into two separate categories. Single-stage shock sensors usually only detect hits or breaks. On the other hand, dual-stage models go off due to even the slightest of vibrations. Thus, they can activate your alarm when a cat goes by it or jumps up on the roof or hood of your car.

Nowadays, all cars have single-stage impact sensors. As for dual-stage sensors, they are usually reserved for alarms that are labeled as extra sensitive.

Microphone Sensors

Just like impact sensors, microphone sensors can also notify you when someone breaks your window or hits your car. They react to sudden noise, meaning that the sound from a bump or window break will set them off.

To ensure that these sensors don’t go off at the regular noise one can hear in a bustling city, companies make them using a unique detecting technology. Namely, these sensors detect sudden changes in the level of noise around the cars.

Thus, they won’t activate your alarm just because a car passes by. Instead, the sensors will just detect sudden loud sounds, especially those that sound like breaks or bumps.

Tilt Sensors

Although most people imagine thieves breaking their car doors or picking the lock to steal their car, some of them can get a bit more creative. For example, many car thieves steal your car by towing it and taking it to a remote location.

To avoid the same fate, you can install a car alarm with tilt sensors. They will discern any tilting and suspicious movement of the vehicle and have the alarm go off as soon as it occurs.

Interestingly enough, these sensors usually use mercury to detect any vehicle motion. If the car tilts, the mercury will move to one side of the sensor, causing it to go off.

Proximity Sensors

Last but not least, car alarms always come with proximity sensors. They detect anyone passing dangerously close to your vehicle, be it a human being or an animal, making them perfect for protection. However, they can also trigger a lot of false alarms.

For instance, your alarm can go off because someone passes by it in the parking lot. Similarly, it can activate if a cat or dog scurries under it or a pigeon flies over it. In some high-end car alarm models, these sensors can even be triggered by the wind.

Common Car Alarm Triggers (Besides Thieves)

As you can probably tell from these sensor descriptions, false alarms are a rather common occurrence with most car alarms. Regardless of their modernity and sophisticated design, the sensor can easily go off by mistake. In addition, the alarm might also go off to notify you that something is wrong with your vehicle or one of its components.

Here are some of the most common car alarm triggers (excluding thieves trying to break into your vehicle).

Accidental Touches

When you leave your car parked on the sidewalk or in a crowded parking lot, someone might accidentally touch it while passing by or trying to reach their own vehicle.

This touch doesn’t have to last long or be particularly harsh. In fact, even a light brush with one’s leg or shoulder can trigger a sensitive proximity and motion sensor. The same is true for any animals going by, as the alarm cannot differentiate between them and humans.

Strong Wind

Talking about light brushes, strong winds are among the most common causes of seemingly random car alarms. As auto theft has increasingly become a major problem, auto companies have risen to the challenge, making their sensors more sensitive than ever.

Unfortunately, such highly sensitive sensors come with a significant downside. They’re much easier to trigger. While this is good for detecting intruders, it can be problematic if you live in particularly windy areas.

Thankfully, some car security systems allow you to reduce the sensitivity of your sensors, increasing the effort needed to trigger them.

Opening the Door With Your Key

Even though car alarms should go off when someone tries to open the door without a key, they can also activate when you unlock the door yourself. In most cases, that occurs due to a malfunctioning remote key fob.

Luckily, this issue is incredibly easy to fix. In most instances, all you have to do is get a new key fob or fix the one you already use. Which solution you’ll need will depend on the exact key fob issue you are dealing with.

Low Battery

A dead — or dying — car battery will also trigger your car alarm. In newer car models, the alarm will also be accompanied by the battery indicator flashing red (low voltage) or black (dead battery).

If you suspect that your battery is dying, you can easily check by measuring its voltage. If it’s low, you will need to recharge it.

Other Battery Issues

Have you checked your battery and found that it is charged after all? Well, you shouldn’t disregard it as a culprit for triggering your car alarm just yet. Before you do so, you ought to inspect it thoroughly.

For example, if your battery terminals are rusty or damaged, the battery won’t be able to power your vehicle as usual. As a result, your car alarm could pick up on that issue and notify you that your battery is dying.

In order to prevent that, you should check the battery fully. Tears, rust, and damage will be clearly visible, so you will be able to tell if you’re dealing with this issue.

If you find any visible signs of rust, you will likely be able to get rid of it with a wire brush and any battery cleaner on the market. But if the rust is extensive or there is additional damage, make sure to take the vehicle to a mechanic right away. By doing so, you will prevent more severe problems in the future and ensure your vehicle is safe to operate.

Faulty Door Locks

As already mentioned, particular sensors control your car door locks and go off when someone tries to forcefully open the vehicle. However, if there are certain issues with the locks themselves, the sensors can malfunction and send signals even when there is no danger.

Generally, the alarm goes off if the sensors in the locks get damaged due to exposure to the elements. The same occurs if the wires that connect the sensors to the locks get worn or tear.

If the tears in the wiring are triggering the alarm, you will probably be able to fix the issue with protective grease sealant. However, it’s best to take your car to a professional instead. That way, you will ensure they find a good long-term solution that will prevent similar problems in the future.

A Malfunctioning Alarm

It goes without saying that your car alarm can go off because the alarm itself is malfunctioning. Usually, that happens due to incorrect installation (i.e., missing a crucial step in the installation process).

If you suspect that the alarm is faulty, you can take it to the car shop employee that helped install it. No matter what the issue is, simply reinstalling the alarm should be enough to solve it.

Summing Up

Car alarms can protect your vehicle from theft and vandalism, as well as notify you if some parts of your car need urgent attention. However, alarms aren’t perfect, so they can go off even when there is no immediate danger. In fact, just an animal passing by or some wind can set it off, creating unnecessary and annoying noise.

Hopefully, this guide helps you understand car alarms — and how they work — better. If you are experiencing frequent issues with your alarm and can’t pinpoint what’s causing them, it’s always a good idea to take the vehicle to a professional. By doing so, you will ensure the problem is actually addressed and resolved.

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