Why Do Car Alarms Go Off Even When Vehicles Are Unlocked?

Car alarms are some of the most efficient safety tools. For one, they can stop burglars from stealing your vehicle or personal belongings by alerting you to any immediate danger. However, as useful as they are, even car alarms can malfunction.

Sometimes, they can go off when your car is unlocked and you’re just trying to get in. Even worse, alarms can start blaring exactly as you unlock your car, making it seem like you’re the one stealing something.

If you’ve ever experienced something similar, stay tuned. We’ll reveal why car alarms malfunction from time to time, and what it means when they go off when your car is unlocked.

1. A Faulty Key Fob

All keyless car owners have a key fob — a tiny device that lets you lock and unlock your car with a single push of a button. At its core, the fob works like a short-range radio transmitter that sends signals to your car.

If the fob is malfunctioning, this signal might not be properly read by your car’s receiver unit. As a result, the car alarm could see you unlocking the car as an intrusion and go off.

Luckily, this type of problem usually has an easy fix. You simply have to replace the battery inside your key fob. Alternatively, you could also reset it. In case your alarm still goes off, it is best to look at other possible problems that might be causing it to malfunction.

2. Malfunctioning Door Key Sensors

During rainy and cold weather, the sensors located in your car locks can get damaged and start malfunctioning. The damage occurs when one of the sensor’s wires gets cut or thins, mostly due to water seeping inside the lock actuator connector.

In some situations, sealing the actuator with protective grease might be enough to solve the issue. However, in case the problem is more severe, it might be best to take your car to a mechanic. That way, you’ll know exactly which door lock has been causing trouble, and the mechanic will be able to replace any faulty parts.

3. Low Battery Level

As you probably already know, a low battery level can cause all kinds of mishaps in cars. Thus, it shouldn’t come as a surprise that it can also make your car alarm go off when you unlock your vehicle.

Although not many people know this fact, most alarms will notify you when your car battery is running low. Thus, if you turn on your ignition with a low battery, your car alarm will immediately let you know that something is wrong. When you combine that with the noise the ignition makes with a low battery, you’ll know exactly what needs fixing.

So, next time your alarm goes off as soon as you unlock or start your car, check the battery right away. If you see that it’s low, you’ll either have to jolt or replace it altogether. After you do, the alarm should go back to normal and only go off at the sign of real trouble.

4. Rusty Battery Terminals

Even if your battery isn’t running low, it could still be causing your car alarm to go off at random. Namely, if the battery terminals are rusty, the battery itself might not be able to properly power your vehicle and all its parts. As a result, the alarm might interpret this situation as your battery being low and go off when you least expect it to.

Fortunately, you will probably be able to get rid of any battery rust. All you need are a wire brush and any commercial-grade battery cleaning agent you can get your hands on.

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However, if the rust is severe, i.e. if it has already started eating away at the metal, it might be too late to save it. In such a case, it’s pivotal to ask a professional for help or to replace the entire battery as soon as possible.

5. Wiring Issues

Sometimes, it is not your sensors or locks themselves causing car alarm trouble. Instead, it could all be due to the electrical wiring that links to one or several of these components.

Now, diagnosing wiring issues is easy, since they are always accompanied by various symptoms. For example, if your headlights also keep flashing at random or your horn acts up for no reason, it is safe to assume you have circuitry problems.

In such a case, it’s best to let a professional handle things for you. They’ll be able to pinpoint the problematic wiring without much trouble and make all the necessary repairs.

6. A Faulty Car Alarm

Of course, your car alarm might be going off even when your car is unlocked because the alarm itself is faulty. In most cases, the alarm goes off because the entire system has been poorly installed.

If you have installed your own alarm system, take another look at the instruction manual. You might have missed a crucial step or done something incorrectly, in which case you can quickly rectify the situation.

Alternatively, if a mechanic or car shop employee installed the system for you, you should go back and have them double-check it. In the vast majority of cases, a simple reinstallation will solve all your problems and ensure your alarm stays quiet when you unlock your doors.

Final Thoughts

As you can see, many factors can play a role in a faulty car alarm. Surprisingly, most of them are not connected to the alarm system at all. Instead, they happen because of other components, such as your battery, key fob, and different sensors. Of course, installing the alarm system improperly can also lead to all kinds of trouble.

Whatever the cause, the best way to ensure your car alarm functions properly is to have a professional check it. They will be able to find the issue quickly and save you from any awkward car alarm moments.


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