Why Does My Car Alarm Keeps Going Off?

Sometimes, the car alarm keeps going off for apparently no reason. It’s a common problem for city dwellers. More than 90% of the time, the car gives false alarms. It could be a passing van or a dog jumping on the hood triggering that deafening, maddening sound.

Why does this happen? Well, there could be various reasons. Knowing about them will help you get rid of this annoying problem.

Car Alarm System: How Does It Work?

A car alarm system is a type of security device that helps to take measures to protect cars when detecting signs of being broken into by thieves. The system usually protects the car by making alarm signals with horns and lights, preventing the car from starting and sending a notification to the car owner… Depending on the structure and settings, each alarm system will have different functions.

About the principle of operation, if any door or hood is unlocked abnormally, the battery terminal is removed, or the car door is broken… the sensor system will transmit a signal to the ECU… After processing, the ECU will issue an order to activate the alarm system. At this time, the siren sounded, and the car lights flashed continuously. In some systems, the ECU prevents the vehicle from starting.

A normal alarm system is when we unlock the car illegally. What is illegal car unlocking? That is, unlock the car with a key-breaking tool or something that the car detects at this time, and the car will alarm. When we unlock the car with the mechanical key without using the control key. At this time, the car will mistakenly think that the door has been opened because the thief breaks the lock. For Smartkey, the car will alarm when we use the mechanical key. Some cars will know that the key next to it won’t sound. 

Why Car Alarm Keeps Going Off?

Learn about five causes that make car alarm going off for no reason, apparently. We’ve also suggested some solutions so that you don’t have to pay a visit to the service shop.

Malfunctioning key fob

The key fob is a small plastic controller that ensures secured access to your car. It also unlocks doors and jumpstarts the ignition system. You can say goodbye to the traditional locking and unlocking the car door with a key because the key fob lets you do it with the push of a button.

car alarm going off for no reason
Changing the fob’s battery could be the solution. (Photo: itstillruns.com)

A malfunctioning controller cannot send the signal properly to the alarm system, resulting in car alarm going off for no reason. You can change the battery, reset the fob, or scan with a code reader to solve the problem.

Unclean hood latch sensor

When the hood latch sensor collects much dirt from road grime and engine grease, it does not function properly. Then, it often triggers a false alarm. The sensor is an effective device that protects your vehicle from theft and damage. It also prevents unintended hood opening. So, you should keep it clean not only to keep the annoying alarm sound at bay but also enhancing the car safety. Use a brake cleaner and cleaning brush to clean it.

Poor connection of the hood latch

If the car alarm keeps going off even after cleaning the hood latch sensor, the problem could be a defective hood latch connection. It can also set off false alarms because the sensor cannot respond properly to the given commands. This issue could also affect the control unit, leading to showing incorrect readings such as turning the airbag light on when there is no real problem with the airbag function.

The sensor is located near the headlights. Disconnect it and then connect it again to make the connection work.

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Low level of the battery

One of the functions of the alarm is to warn about low battery levels. If you try to switch the engine on with a dying battery, the alarm will go off. You should check the battery with a voltmeter if the car alarm starts clamoring without any evident reason. The battery needs a replacement if the reading shows less than 12.6 volts.

car alarm keeps going off
Test the car battery to see if it is running low. (Photo: Foresee)

Rusty battery terminals

It’s another reason for the car alarm keeps going off. Due to the worn-out terminals, the battery cannot supply enough power to different car parts. The alarm sensor can interpret the condition as low battery and set off to warn you about it.

How To Stop My Car Alarm From Randomly Going Off?

Although useful, the alarm system is sometimes a nuisance for many people. They often sound sudden, difficult to turn off and startle everyone around. However, the alarm also helps to ensure the safety of the car. Here are some ways to fix the problem when the car alarm keeps going off.

Open the driver’s side door

In case the alarm system keeps making a sound and the remote control does not work, you should use the key to open the driver’s door. Normally after the door is opened the buzzer will turn off. If the door is open, try locking it and then opening it again with the key.

Remove the system fuse

Find the alarm fuse in the fuse box, remove it, and put the fuse into a plastic bag or storage compartment for safekeeping. If you cannot locate this fuse, then you can unplug the fuses in the box one by one until the alarm goes off. This will not cause damage to your vehicle, but note that you need to reinstall the fuse in its correct position if not the alarm fuse.

Unplug the battery

The alarm also works on the vehicle’s electrical system. So, if after you do the above, the alarm is still on, you should remove the battery terminal. Open the hood, locate the battery, and use a wrench to open the negative terminal of the battery. Wait a few seconds and then reinstall the battery post. Or to make it easier you can unplug the connection to the buzzer.

Sometimes this is a fault related to the electrical part as well as the sensors located inside the car. Therefore, it needs to be checked by machines, as well as car mechanics who will check the ic, and switch fuses from there to know if there is a fault, short circuit, or broken wire at any part.